Why not do one of those half and half holidays where you start off in Orlando for a week and then go to the beach for the second week?
Yes there are rides in the theme parks that your children won't be able to go on, but equally there are lots of rides that they will be able to go on, aimed at the younger children. (For example, in Islands of Adventure there is a 'Cat In The Hat' section with all the rides and restaurants themed around the books). There are also lots of other things to do in the Orlando/Kissimmee area, my children really enjoyed playing Mini Golf (we'd called it crazy golf, but the courses over there are SOOO much better than here!), then there are the water parks, helicopter rides, airboat rides, Gatorland (alligators!). And I'm sure that most 7 and 5 year olds would get a lot of pleasure out of seeing some of their favourite characters at the theme parks!