The Crenshaws were having a family argument. Cary and Jan, the children wanted to go on the breakfast horseback ride. Arthur and Ann, the parents, couldn't see bouncing on a trail for a hour just to get to the grub wagon, and more to the point, they couldn't see bouncing back to the lodge with stomachs full of flapjacks and juice. They lobbyed for the river raft trip.

But the kids won out. Ann hurried off to the lodge store to stock up on rubbing alcohol. Arthur walked to the recreation desk and popped down $40 to reserve four horses - timid ones, he insisted.

"There was a time," Arthur Crenshaw recalled, "when we could have afforded both the horses and the float trip. This year we had to choose. We have to be more careful about what we spend now." He paused for a minute, carefully folding the receipt for the trail ride and placing it in his wallet. "I think the kids will like this." A trace of concern around the eyes, apprehension, mild panic. "Do you happen to know anything about riding?" he asked.

Lots of folks traveling through this panoramic mounting valley in northwest Wyoming are having to make choices like the Crenshaws. Stung by inflation, many vacationers here are buying less and simply sightseeing more. Gift shops in Jackson, the western-style resort town in the park's south entrance, report distressingly few sales in June of generally popular items such as hand-woven Indian baskets and cowboy hats. Restaurant managers, too, complain about a falloff in business.

One reason may be people like Alan and Judy Marchick. They have stopped eating in restaurants. Instead, they now eat outside them - directly outside - dining very visibly on homemade sandwiches to protest the price of eating out.

"They're asking $2 for a hamburger in there," said Alan, seated on a bench outside Jackson Lake Lodge, the park's main hotel. "It may not be totally their fault, but it's still ridiculous."

The slump in vacation spending in this part of the country came as a surprise to businesses here that had been banking on early reports of increased summer travel this year.

"Most of our concessions - gift shops, food stores, day trips - are soft about 7 percent," said Bernard Illiff, general manager for the Grand Teton Lodge Co., the park's chief concessioner. "We had expected about a 10 percent increase. But people get here and then they don't spend much. They don't have that extra buck like they used to."

Nationwide, people are, in fact, traveling more. According to the U. S. Travel Data Center in Washington, domestic travel is up about 10 percent. But the evidence here suggests that vacationers may be spending less at their destinations - except on lodging. Also, it appears that people may be driving less to out-of-the-way places and flying more to easily ac-cessible vacation spots, taking advantage of discounted air fares.

Watching what people are arriving in, it is apparent that many still have large, up-front investments in vacation travel. The number of so-called recreational vehicles - motor homes, trailers, campers and vans - almost seem to outnumber plain old automobiles. On the outside, these self-contained homes-away-from home often carry lounge chairs, small boats and bicycle racks and such nicknames as "Nomad," "Dreamer," "Jamboree," and "American Clipper," bespeaking a traveling life of ease, freedom, fun and convenience.

William E. Miller, a 59-year-old teamster from Beaverton, Ore., owns an RV, a $10,000 Coachman model. He says he bought it to go on short fishing trips and long vacations. He talked about it while casting for Mackinaw below the Jackson Lake Dam one day last week. His feelings were representative of the feelings many RV oawners have about their vehicles.

"Inflation didn't make a difference wahen I bought the van and it doesn't make a difference now," he said. "What me and my wife both work for is vacation time. With the van, we can take off anytime we like and not worry about hotels or anything like that.

"A lot of people are running around here saying prices are too high. Of course they are. But I guess you have to go along and forget about it. We just figure to hell with the price of gas."

Like Miller, most Americans stubbornly resist cutting back on vacation time and some vacation costs, no matter what happens to the cost of living. National consumer studies estimate that the average family sets aside about 4 percent of its budget for entertainment and vacation travel. It is not a major expense when compared to the amounts spent on food and housing. But it is an almost sacred one.

"Travel is viewed more as a necessaity than as a discretionary, luxury-type of expenditure," said Steve Muha, chief researcher for the U. S. Travel Data Center. "Ask people why they take a vacation and they say, 'Have to.' One of the reasons travel expenditures are hard to measure, in fact, is that people don't even remember what they spent."

Camped by a quiet mountain lake, George Rothermaier and Sally Helm, both from San Diego, talked about the ways they ahd tried to cut costs at home. George sold his car this year and started cycling to work, figuring he would save %2,500 a year on insurance, gas and maintenance. Sally shopped more agressively for sales and bought such items as toothpaste, shampoo and paper plates in bulk quantities when she found a good deal. But when it came to their annual camping trip, George and Sally never gave it a second thought.

"It's hypocritical in a way," said George, a social worker who is currently unemployed. "I feel as if I'm perpetuating the situation by not changing. But whether it costs $400 for this trip or $450, it wouldn't make much difference to us. We'll pay a buck per gallon for gas for whatever it takes to go camping rather than stay at home and pay $50 an hour for a shrimk."

Which isn't to say that it would be very easy tocut back on camping even if they wanted to. Chuck Pullen, a 23-year-old graudate in Pharmacology from Santa Barbara, Calif., has been trying to see the USA by motorcycle on $10 a day, but he isn't making it.

"I don't know if it's possible anymore," said Pullen, parked at a camp-ground here named Gros Ventre (literally, big belly). "Prices are outrageous, especially gas. And here I'm paying $3 a night for a plot of dirt and a picnic table. I can't even get a hot shower. I have to go down the road to the coin operated showers and spend about $1 more, depending on how fast I can get clean."

A few here are finding it possible to travel on a shoestring budget. But it takes muscle, healthy lungs and patience, say Jerald and Debra Byrd, who are bycycling from Portland to Washington, D. C. this summer. They arrived in the Tetons last week, 1,500 miles into their trip, looking lean and tap. The trip so far has cost them only $4 a day.

They had just stopped in Jackson to buy supper, which consisted of two potatoes, chilli, beans and corn. Total cost: $2.50.

The purpose of the trip, they said, is to scout for a new place to live - away from the pollution, the congestion and the high cost of living they had known in Houston. "Where I worked," said Jerald, formerly an instrument repairman for B. F. Goodrich, " we'd get a pay increase every year, but it didn't help much. The grocery stores knew when the raises were coming; they'd just raise prices."

He said he has like Oregon best so far, "because it was the cheapest and friendliest." Whats the least expensive place they'd discovered? A restaurant in Baker, Ore., which still serves coffee for a nickel and all you can eat for breadfast for $1.50.

The people interviewed here, like those in Santa Rosa, Calif., and in Reno, Nev., each had their own favorite explanation for the cause of inflation. But in this setting they tended to philosophize more about the problem, seeing inflation as just part of a larger and distressing picture of the economy and of human nature.

Jerald Byrd, the bicyclist, blamed inflation on selfishness, on "people taking advantage of other people. . . . I really don't see any change," he said, "until people's attitudes change, until they become less selfish. They will have to stop looking out for themselves and start looking at the whole country."

Others tended to lump inflation in with concerns about pollution, over-population, deterioration of the cities, big government and big business, and they spoke of a general dissatisfaction with the overall state of affairs in America today.

"It's not a problem, it's a symptom" said George Rothenmaier, the social worker, "symptom of our system not working, "a sympton out of control. Probably what is needed is a crash. it seems to me the measures now being taken are stopgaps."STChuck Pullen, motorcyclist, also spoke about inflation being "interrelated with everythig else," and something that "can't be solved piece by piece." "I hope it never comes to revolution," Pullen said, mulling over the thought, "at least not until I get my motorcycle paid off."