Mrspink we have been to Florida with our 2 boys when they were 5 and 3 and again at 7 and 5.
I have not been to Busch gardens, so can't comment, but IMHO the very best park for small children in Orlando is the Magic Kingdom. There is so much to see and do - we went twice both holidays.
The Animal Kingdom is not a patch on the MK for entertainment value, but then we live very near to Woburn Safari Park and Whipsnade Zoo, so are pretty much animaled up here in the UK.
Seaworld is a good choice too. The Disney waterparks are great for small children - Typhoon Lagoon is probably better for children as small as your 2, or as others have said, Wet and Wild is good, I haven't been there for years though as we buy multipark tickets for Disney.
Kennedy Space Center is incredible, but not really ideal for small children - ds2 slept through the tour when we went when he was 3.
If you search the board for Hulababy's comments on Florida you might get some useful info - she has a 5 yr old DD and has taken her to Florida a couple of times
HTH