There ARE other places to go than Disney, and if you go there, just say "we went to Vermont last year and are going to Texas next winter."
If you don't, well, "we like it there" works.
We've gotten it occationally, and we always say "its really the perfect vacation for us right now. It handles kids well. There are a lot of decent restaurants. We enjoy the atmophere, the hotel pools are wonderful. There is always something to do - but if you feel like relaxing you can do that, too. Its relatively clean and safe. When the kids get a little older, we will do some more challenging travel with them, but we will continue to go to Disney for the great golf courses and resorts. Did you know Disney has 99 holes of golf, offers bass fishing and horseback riding, a resident Cirque du Soliel troupe, and has two full service spas? It isn't just theme parks."
By the time we get done, they are booking a trip themselves.
The complaints are "but what about the crowds" ("Oh, we never travel during busy season.") and "its so expensive" ("yeah, it is, we are lucky to be able to afford it, and there are some tricks to keeping it reasonable.").