Thanks for the input guys!
Dh and I talked about it tonight and he thinks Disneyland is a viable option now that we know the boys will still have a ball and be able to go on rides. He's only balking at the cost to head to the USA so we've compromised on Hong Kong Disneyland (especially because we are in Nth Qld so we have to trek south to Sydney usually to catch international flights). Lulu, I checked out the Disney website for height restrictions and it looks like our 3 are tall enough to ride everything bar 1 or 2 of the biggest rides! Thanks for the suggestion!