Atmopshere: Casual sophistication, friendly. Kids welcome and taken in stride, even when they walk around the room while waiting for dinner to appear. s

Hours: Monday through Friday, Lunch 11:30 to 2:30, Dinner 5 to 9. Sunday brunch only, 11:30 to 2:30.

Price Range: Entrees $4.25 to $5.50.Sandwiches $3.95 to $4.25. Children's dinner half-price for half portion.

Reservations: Not necessary.

Credit Cards: Visa, American Express, Master Charge.

Special Facilities: No booster seats but plenty of telephone books, says management. Call ahead to Canterbury House, 296-5576, for elevator access for wheelchairs.

The decor alone might be reason enough to try the Polo Pub, the below-sidewalk restaurant of the Canterbury House apartment-hotel. Its one small room has a quiet, clubby atmosphere with black banquettes against dark, grey walls hung with action photo blowups of polo matches. Polo mallets and riding helmets hang above tables laid with white cloths and maroon napkins.

"I'm tired and hungry," announced our 9-year old as we parked in front of the canopied entrance on a street that reminded us of New York's upper West Side. So, a practically empty dining room was a welcome sight, as was the handwritten autumn-winter menu, promising spirit-reviving New England clam chowder and Polo Pub chicken curry.

A considerable wait for our appetizers was partially offset by warm sesame-topped french bread accompanied by mounds of fluffy butter, and a round of backgammon, using one of the sets kept at the entrance.

Stuffed mushroom caps, for $2.25, was seven large mushrooms brimming with shrimp and crabmeat but drenched in a rather bland savory sauce. The menu's only other appetizer, cheese and ham puffs, for $2.25, was requested without ham. They came, four large croissant-like pastries, wonderfully flaky with a melting swiss cheese interior. Enough for two people, the cheese puffs were worth the wait for the special order.

At first, The Polo Pub didn't seem family oriented; no children's menu, only a few tables for more than two, and no milk available for a youngster's requested beverage. But our fourth-grader had his choice of the soup and sandwich special, a selection that suited him fine.

The clam chowder he ordered, laden with clams floating in a milky, buttery broth, was redolent of some of the best found farther north. It was so good, we ordered another to share. His sandwich, the English dip, was lean, tender roast beef on sesame french bread served with good beef broth for dipping. The special is $4.50 and there's a choice of four sandwiches, including chicken curry in pita bread.

Half portion entrees at half-price are also available for children.

The menu also boasted a soup du jour, $1.50, but there wasn't any. More disappointing was the fact that no one knew what was in the casserole crock offering. The daily casserole, prepared by the day's cook, was not identified by a note, said our waitress. Presumably, it was indecipherable by eye or taste.

There were good surprises. Polo Pub chicken curry, $5.25, is tender and spicy, accompanied by a tray of five condiments: coconut, raisins, silvered almonds, mango chutney and chopped onion. The scallops in the coquilles St. Jacques, my husband's choice and $5.50, were succulent and cooked just right. But the sauce was over-sherried.

Entrees come with a house garden salad of crisp, fresh greens and spanish onion garnished with egg and tomato quarters.

Our teen-age daughter could barely finish half her order of clams in white sauce with spinach noodles, a generous serving at $5.25. But a preponderance of olive oil almost drowned out any good qualities in that dish. And the clams, whch appeared tender in the chowder, were chewy atop the pasta.

Water glasses were refilled promptly. Our service was unhurried and solicitous, despite the fact that the restaurant had only one waitress.

Whatever had gone awry during dinner was soon forgotten at dessert. The menu offered amaretto cheese cake and a special, each $1.50.

"Chocolate mousse!" both kids echoed when the waitress identified the special.

"Why don't you share one? It's real rich, usually people can't finish one.

Then, if you want more, I'll bring another," she suggested.

Since the mousse turned out to be chocolate mousse pie, thoughtfully divided in advance into two, large, rich slices, the kids were glad they took her advice. Delicious, mysterious layers of chocolate blended between crust and filling.Tiny chocolate chips turned up at every bite. And the amareto cheese cake, exuding almond fragrance, was fresh and just the right creamy consistency.

Clearly, desserts and appetizers are winners at The Polo Pub. Corrected sauces could go a long way toward improving the entrees, which are served in such generous portions that most dishes could be shared by two.

Our bill for four, including tax and tip, was $41.72. We left, with the remaining half of the English dip wrapped for the next day's school lunch.