Margaret,
Both of these Epcot restaurants are excellent! Below are comments about both, but note that Bistro de Paris is not a
Disney Dining Plan restaurant. When you make an Advanced Dining Reservation (407-939-DINE or 407-939-3463) you can confirm if that is still the case.
Chefs de France is reminiscent of a sidewalk restaurant in Paris, bringing classics like Croque Monsieur, crepes, and more substantial entrees. It is open for lunch and dinner.
Bistro de Paris is a more formal, white table cloth, experience. The cuisine is exceptional, with a shorter but more than adequate diverse set of selections. It is only open for dinner.
Bistro is the higher end experience, but Chefs de France is still one of the better meals at Walt Disney World.
With an 8 year old, I strongly suggest Chefs de France. It has a Children's menu (unlike the Bistro), and has a wide expanse of windows that look onto the World Showcase walkway and lagoon. It offers up a great view of the action going on outside!
Bon Appetit!