The full name of this eatery is "Huey, Dewey and Louie's Good Time Cafe." Besides having the longest name of anything in Tokyo Disneyland, it is the only restaurant in Toontown (although there are a few snack stands about). It is a counter-service restaurant, and there is lots of outdoor seating but no indoor, and not a lot of shade.
Kids will probably appreciate the food most. The most popular item on the menu is a pizza shaped like Mickey Mouse's famous silhouette. Pizza comes in two varieties: combination and fruit, the latter of which is probably more appropriate as a desert.
Huey, Dewey & Louie's Good Time Cafe isn't my favorite place to eat in Tokyo Disneyland. It's almost always very busy, and—despite the fact that the pizza is shaped like Mickey Mouse—it's more expensive than other pizzas at Tokyo Disneyland and my least favorite taste-wise. If you're interested in pizza, you'd be far better off taking a short walk over to the Pan Galactic Pizza Port, which, in addition to having better tasting pizza, has plenty of indoor seating (important on those sunny summer days) as well as some neat "entertainment."