We went the last week of April 2003, and it was surprisingly warm. It was in the mid 80's all week. Crowds weren't bad, from what I remember. We had a 4 yr old and 7 month old at the time, and were also there with my niece (11) and nephew (9). I think everyone was able to do what they wanted, and that was without ANY kind of plan! (Obviously I was not involved in the planning of that trip!). I'd say that April should still be nice time to visit. Maybe someone can relay their more recent experiences? HTH
Kathy