W.M.
We took our kids to Disney World 2 yrs ago. During that trip we did 2 days at Sea World - I wish we would have done more! We found Sea World had better food, more shade and was less crowded than Disney. At the time, there was also a deal where you brought back your first day's ticket and got in the second day free (we went in late May). We have thrown around the idea of going back and this time skipping Disney and going to Discovery Cove.
Depending on your kids ages, I would suggest doing the "free" stuff - Disney's Boardwalk and Universal Studios CityWalk.