Open 24 hours a day seven days a week. Full carry out service. No credit cards or checks accepted. Ample parking.Accessible to the handicapped.

It may no longer be undisputed king of the highways, but Howard Johnson's is still a good place to visit with kids. The orange roofs are still there. So are the 26 flavors of good ice cream, the low-priced children's platters, free birthday cake and lots of high chairs.

Frankly, for adults not all the food is so good. But if you stick to the staples - frankfurters and baked beans. New England clam chowder, fried clams, or fried chicken, you can enjoy yourself while the children have a grand time.

We took our two children for Sunday supper to the Howard Johnson's on Landover Road (Route 202) in Prince George's County, just off the Baltimore-Washington Parkway. Susan, our 3-year-old, remembered being there before and insisted on wearing her best blue dress and party shoes - she knew she would have a good time.

For supper Sue chose the "Super Sailor" - fried clams, French fries, roll and butter, ice cream and orange drink. It cost only $2.10 for what looked to us like an adult-sized meal. Sue managed to eat a lot of it. She was willing to share the French fries, but took home all the left-over fried clams in a doggy bag, and finished them the next day.

For Dan, 1 1/2, we ordered a "Fearless Fido," for $1.45 - a hot orange drink. Dan liked the hot dog so much so that he ate it all and left the potatoes and roll, which is quite out of character. He liked the orange drink so much that he learned to stop blowing bubbles and use a straw properly for the first time.

Unfortunately, we were less enthusiastic about the meals for adults. My husband's beef Burgundy, $4.25, was "all right," but no more. In fact, after eating it, he ordered a cup of clam chowder, which he had enjoyed in the past, and still thought was very good.

I ordered the roast-turkey which turned out to be turkey roll with very salty gravy, and a peculiar chewy texture. Not good, even for $3.60.

The most expensive entree on the menu is sirloin steak for $5.95. The cheapest - and probably best choice except for the clams - is grilled hot dogs with a pot of baked beans and brown bread, for $2.45. A complete dinner, including soup, dessert and beverage, costs $1.25 on top of the entree price. There is also a range of sandwiches, salad plates and hamburgers, costing about $2 to $3.

The children's menu at Howard Johnston's lists nine different meals - all with desert and beverage - ranging from a peanut butter and jelly sandwich, for $1.45, to fried chicken, potatoes and vegetable, at $2.25. The menu itself is an educational comic book, explaining the metric system, which children can take home with them.

Parents of really young children will be amazed to find that this restaurant sells jars of strained baby food for 25 cents each.

If you can afford the calories, the thing to eat here is ice cream for dessert - or any time, for that matter. It's good and creamy with lots of fresh fruit. The children each got a dish with their meals - strawberry and cherry. If you buy the dish that really is plenty for two. Sundaes and sodas cost $1.10. A banana split - gigantic - is $2.50.

The waitress brought extra spoons and dishes so my husband and I could share the children's ice cream. Earlier, she brought out drinks and rolls quickly when some of us couldn't wait for the food to get to the table.

The bill for the four of us came $12.98 plus a tip for the good service.

At the table next ot ours a boy was celebrating his birthday with three other children and his mother. The children, who appeared to be about 8 to 10 years old, consumed large plates of fried chicken, which they said was great, before tackling birthday cake,lollipops, sundaes, and sodas. The cake and lollipops were free, along with the birthday boy's dinner. Any child can get the same free goodies if parents register the birthday in advance.

Altogether, there are 10 Howard Johnson's restaurants in the Washington area - a few less than several years ago. Five are in the Maryland suburbs, four in Virginia, and one in the District, which is probably the best-known of them all. It's located in the Howard Johnson's hotel on Virginia Avenue NW, which served as a look-out spot for the burglars who broke into Democratic national headquarters in the Watergate, just across the street.