The problem was that we'd both promised our spouses we'd get the children out of the way for the weekend. Two of us had the problem.

Mathematicians have a way of dealing with problems that they call the Elegant Solution. Having tried to cope with problems during our parenting years by turning to psychology, history, political science, literature and chemistry, it was time to turn to mathematics; at least the terminology was attractive.

We decided to turn the weekend into a celebration of the International Year of the Child and to take the children to another country for the weekend.

Since Sarah, three, couldn't speak French, Paris was out. Besides, it seemed an Excessively Elegant Solution.

The answer: Toronto. Cooler than Washington. Only an hour and a half away by plane. Inexpensive, especially since the American dollar now fetches about $1.15 worth of Canadian money. Cosmopolitan but still charming. Foreign enough to delight but not to startle. Spotless and firendly, the city has been called "a clean New York." Fare: about $200 round-trip for parent and child using Allegheny's "Freedom Fare" or "Flexible Flyer" rate.

Noon Saturday, hand luggage and a bag with snacks in tow, the four of us - Sarah, nine-year-old Libby and one parent each, ages undisclosed - arrived at National Airport; experienced travelers, we had checked to find that the flight served no food more substantial than peanuts. By 3 p.m. we had checked into a grand downtown hotel, the Royal York. Cost of a room for parent and child: $35 Canadian, thanks to a special weekend rate appropriately called "The Spoiler."

Within an hour we had arrived at the focal point of the trip, a grassy, sprawling fantasy land for children and adults called Ontario Place. Built on - and in some cases over - Lake Ontario, the three man-made islands of Ontario Place constitute a 96-acre playground for mind and body. Fourteen hours a day every day (eleven hours on Sunday) for the entire summer, Ontario Place streams with people of all ages. Senior citizens get in free, others pay 50 cents to $2.50, and all activities are free once you've paid your admission.

You come upon it in a rush of grounded warplanes for climbing and gun turrets for unleashing aggressions, of a battleship for exploring, of paddle boats and yachts and dazzling white iron bridges and stairways. Establishing priorities between Neil Sadaka concerts and marionette shows and rock band concerts, at least we all agreed we hated roller coasters and could ignore the entire thrill-ride section of the park.

First priority was a late lunch. We should have packed another bag, for the cunning little ethnic restaurants cuddling among the islands all seemed to serve the same minimally edible food flavored German, Irish, Chinese or whatever. The rubbery ground meat was peppered and shaped like hockey pucks in the German restaurant, but the geese honking in the lake and the amorous coples on the grassy slopes provided enough distraction to permit the children to down a few bites.

A clown twisted balloons into animals for them while we washed down gummy bratwurst and indifferent goulash with mugs of beer. Next we tried to fill up on Chinese food, ignoring the fact that all the Chinese we saw were eating hot dogs. The Chinese specialty was Bo Bos - ground meat formed into balls, dipped in batter, deep fried, and imbedded in a bright-orange, sweet-sticky ooze that stained my fingers for the rest of the day when I dipped in it for a taste. If you ignored the so-called sweet-and-sour sauce, the deep-fried spareribs were edible and, at $1.35, cheap. Even so, we vowed to stick to ice cream thereafter, forget the food and concentrate on the attractions.

Imagine you are a child and a fairy godmother has suggested you let your imagination run amok to design the world's best and biggest playground. Perhaps someone's fairy godmother did just that, because Ontario Place is a smorgasbord of thrills, small and big.

Oversized, gaily colored pipes serve as crawling tunnels for three-year-olds. A water slide and big pool with revolving water guns pleases nine-year-olds who are generally scolded for splashing around excessively in most pools. There are winding slides, stretching two stories high, that only a child has the courage to attempt. There are 25-foot wooden forts accessible only by scaling rope ladders; an escape slide and tunnels provide a thrilling exit. Inflated rubber mattresses the size of parking lots are favorites for kids in socks who think jumping is great sport.

To relax, we took in the short movie at the indoor theater, whose screen is the same size as the one at the Air & Space Museum. The film, commissioned by the U.S. Department of Commerce, was about the planet - but although the breathtaking photograph was reminiscent of presentations at Washington's museum, it wasn't "Living Plant" but "Man Belongs to the Earth, produced and directed by a Canadian filmmaker, Graeme Ferguson.

The last ride of the day was a thriller - aboard an old-fashioned, working trolley car back to the hotel. By then it was 8:30. As two tired little girls changed into nightgowns, room service delivered their dinner. The waiter took the silver serving cover off with a flourish to reveal a fat cheeseburger. Also on the silver-laden table were a fruit cup without kirsch, two milks, one apple strudel and an extra knife and fork.

The table fit just between the two beds so the girls could fulfill a fantasy they had discussed all day: dinner in bed. A list of emergency numbers was issued. After hugs goodnight, we adults slipped off for dinner at Winston's to celebrate a problem elegantly solved.

We chose Winston's because it's so adult. Nearly 50 years old, it's discreetly lush, Art Nouveau with a vengeance from the wood tendrils curling around the mirros to the silver salt shakers heavy enough to serve as weapons.

Wintstons, has its own game farm and trout farm; it's the only restaurant we know that needs to invent recipes for leftover pheasant (particularly since it has no freezer at all): pheasant cutlets, pheasant quenelles. We knew we would be well cared for, since there's one staff person for each 2 1/2 seats; seven chefs cook for the 120 seats. Winston's is considered so reliable that 16 of its 23 tables are permanently reserved at lunch.

Memories of Ontario Place's frozen hamburgers receded before pheasant quenelles with foie gras and truffle sauce, before oyster and artichoke soup. A phone could be plugged in at the table if we needed to check on our girls between servings of Lake Brome duck - boneless, crisp, meaty - and rack of lamb - marinated, impeccably trimmed, roasted and carved into five double chops for one person. Black Forest cake pulsating with kirsch relaxed every muscle knotted from rescuing toddlers from high places.

Had we chosen to eat less expensively, we were still in the right city. The Clyde's of Toronto is a fine bar and restaurant, all wood and glass and plants, called Bemelman's. The fare is good and the clientele is a cross-section of the city's fashionable folks - photographers, models, television personalities, gays, theater people. For burgers we could have sampled the offerings at Hector's, where the Hollywood folks just finished filming some scenes for a George Peppard-Lee Remick movie called "Torn Between Two Lovers." Or we could have stepped up to the bar at a pub such as Troupers, where over 40 brands of beer from around the world are sold by a barmaid who gives you a "Cheers, darlin"!" as she sets you up with a pint.

When re returned to our hotel, we found a note from Libby resting on a wrinkled Pampers; she had not known how to deal with Sarah's diaper. But everything else was fine. Sarah's daddy carried her back to their room. Libby's mommy wheeled the room service table with most of the cheeseburger intact into the hall. And visions of sugarplums - being British sweetmeats, after all - had new meaning in dreams that lasted until an unwelcome six oclock awakening a.m. led all four dashing to the airport for a seven o'clock flight back to Washington and the spouses who were taking charge for Sunday. CAPTION: Picture, DOWNTOWN TORONTO, AN HOUR AND A HALF FROM WASHINGTON. By The Christian Science Monitor.