One of the important things we teach our students with disabilities is that they need to 'own' their lives, and that includes understanding what they can do independently and what they need to work on, need help with, etc. We're all good at something, and may totally suck at something else. My students know I can do the academic stuff 'no problem', but know I need help cooking. They'll tell you not to ask me to make cookies - I once forgot to put the oatmeal in the oatmeal cookies we were making...
WDW does not ask for a diagnosis, just what issues a person may have that makes it very difficult to wait in a queue. I'm betting your children already know they have issues with waiting in a queue. It's nothing to be ashamed of, so is there another reason I'm missing that you don't feel comfortable talking about what is hard for them in front of them? Kids are smart - they figure out why adults do things a certain way, and pick up on subtle cues we think go over their heads.
I really like your perspective and I have 2 stories to go with it.
One is a child whose parents avoided having him hear any discussions about his issues. He heard them quietly talking and knew they were talking about him. One day, his mom thought he was in a room farther away, he overheard his mom talking to someone else about him being autistic (he had Aspergers). He was relieved - since it was something they whispered about and never talked with him about, he knew he was different, but figured he must be weird or it must be something really shameful and bad.
Another is a story one of my instructors in Nursing school told us that that happened to her. She was caring for a little girl who was dying of cancer. The parents didn't want her to know and had orders all over the medical record that no one was to tell her about it. The Nursing staff didn't agree, but followed the parent's instructions. If she started asking questions, they changed the subject, so she really didn't think she could talk to them.
One day, the girl told the Housekeeper, "I know I'm dying, but I don't think my parents know. They whisper a lot. I've tried to talk to the nurses, but they are not listening. I don't think they know either. I can tell I am getting weaker and someone needs to tell my parents."
She asked the Housekeeper to please tell her parents (Housekeeping staff were about the only people who were not aware of the parents' instructions). Luckily, the Housekeeper told the girl's nurse and everyone, including the girl had a discussion.
So, sometimes the good intentions of trying to hide something from a child lets the child's imagination take over and come up with something much worse than the truth.