It's making me really uncomfortable that people seem to think it's okay to call parents selfish if they don't send their kids on a trip just because they're invited. Regardless of their reasons, they are the parent and it's their choice. It's okay to be disappointed or wish they made a different decision, but is it really okay to insist someone should send their kids to WDW or anywhere else they're invited and if they don't, they're selfish?
Unless they've been sending their kids regularly with other people, this decision has nothing to do with the OP. It's just a parenting decision they've made.
I guess I am going to have to disagree with you and say that the parents are being selfish not letting their kids go away without them. They are more concerned about them being worried then letting their kids have some fun and spread their wings. The parents that are so worried about their teenagers not being watched like a hawk are most certainly selfish. When do these kids learn to grow up? How nice is it to these kids to dump them at college one day never having experienced being away from home? I just don't get it personally. I think EVERY child should have a special adult that isn't their parent in their lives to do stuff like this with because that person will always be someone that a child can turn to if they don't feel like they can turn to their parent.