We ate there for dinner at the end of January, and at that time, it was a 30-day booking window. I called about mid-morning a month in advance and had no trouble getting the time we wanted.
Dinner was delicious. They do accept the DDE, but they do not participate in the
DDP. There is no children's menu, but there were a lot of children in the dining room when we were there. If I recall, there were three, possibly four families that I could see that had young kids.
While we were in the waiting cove to be seated, I did see a family walk up without a reservation, and they were told they would be seated. Marrakesh & Biergarten were not accepting walk-ups that night. So even if other places are busy, Bistro might not be.
The menu is extremely creative, and the service is wonderful. My meal consisted of escargot for an appetizer and the lobster risotto for my entree. DH ordered the chilled crabcake for his appetizer and a sauteed fish for his entree (snapper maybe?). We shared a chocolate dessert that included several small chocolate creations. The only negative we could both say is his fish was either lightly fried or sauteed with the skin of the fish still on. He basically had no choice but to eat the fish skin or destroy the crust on the fish to avoid it. With my lobster, the tough cartilage pieces hadn't been removed, so a few bites were inedible (but you don't know it until you start chewing it!).
Our server was very good about recommending wines we'd enjoy with our meal.
This is also one of the few places on Disney property where you will get a good cup of real, non-Nescafe coffee.
Overall, we'd recommend it, and we'd return. We just might ask more questions about the menu -- oh, and brush up on our French so we can understand better!