Be ready to sweat!
It rained a ton when we were down there. Had to postpone most games. Drink water and be prepared for anything. Great competition though this last year I think many of the teams people thought would do well (ours included)were out somewhere in the middle. Didn't bring our stuff for that week, but whatever. The kids had fun. My son's most favorite game he ever played was there, and we lost. Played the Banditos in extra innings. A real nail biter.
My biggest suggestion as far as Disney goes is to go to DisneyQuest. We unfortunately found it late but it was too fun. One price admission, 5 story arcade. Would have been great on those rain delays.
Which team does your son play for? We've met up with some MO boys before.