US Holiday with young kids

My better half is keen to do a US holiday this Summer. I'm concerned that the kids who are 9, 7 and 3 are still too young for long flights and the orlando/disney scene. What are peoples thoughts on the best ages for kids to enjoy the Orlando experience?
Hotel holidays havent really worked for us in the past so we are usually self-catering/camping holiday people. I see companies like Keycamp are doing US camping holidays now - has anybody tried a US camping holiday. This type of holiday is great for families in Europe but just wondering what the facilities/atmosphere is like on such Sites in the US
Thanks

i am recently back from barbados and there was a family on the plane with 4 young children, the youngest being 3-4 months old. i thought they were off their trolley. they were so stressed all the way home in the plane (8 hours). i really dont think you should go long haul with a 3 yr old. the others are ok. let it until the youngest is 7, the oldest would be 13 then and thats not too old for florida

Hi

I have been to the US before on a road trip around New England with an 18th old, we are going to Orlando in March with same child who will be just 4. I think it depends on whether you get stressed with travelling on not. It doesn't bother me to bring him that distance at all. A good tip I saw was to wrap up one activity for every hour of the flight and that keeps them busy. I did pay the extra to get a direct flight though. I think that is worth it, otherwise it is just too much for them.
Re the camping, I doubt if they do anything by halves on that front. No Frontiers had a camper van park in Orlando on some time ago and it looked class, far better than what you would see in Europe.
I say go for it, god knows this is the time to be taking holidays if you can at all.