Dontcallmebaby....I haven't booked anything in advance this time, but I did book the birthday tea party with the travel agent the last time I went.
This time I've booked independently, so am just recovering from the multitudinous papers that I've got relating to the flight, the carparking, the hotel in Paris, the overnighter near the airport, the RER tickets, etc...
I would say you don't need to book too much in advance. You can contact reception at the hotel and they'll help you book anything you need. The birthday teas are sometimes oversubscribed, but we went in January (was cold, but still good) so we didn't have that problem. I've never been in peak times, so it might be worth looking into that via the travel sites on t'internet.
Also, get used to the idea of queuing. It's part of the experience. The only thing you can do to minimise it is (a) hit the park early morning; (b) get fastrack tickets for the big rides and (c) try not to stress too much about it when you're there.
The characters usually do a couple of mornings and evenings at the hotel, in the foyer, so there's always a chance to see their favourites in a relaxed way. The character meals/teas/breakfasts also help as they eliminate the need for queuing and they get your little one some one on one time with the main characters.
I'm a total queue hater, but we managed o.k. with dd when she was 2/3 and 4 (we got hooked on the ED experience). We explained to her that sometimes you have to queue to see someone or something you really like and she adapted quite quickly.
Catching the buses to the park in the morning is the worst bit, cos everyone pushes and shoves and no-one seems to understand the concept of queuing. Get past that hurdle and it's not so bad from there on in.
Hope you all have good hols....