I have an 8-year-old autistic son, and we have been flying with him since he was four (4-5 times a year). We got a letter from his doctor stating his diagnosis and the fact that he needs special food and drink. Before travel we call TSA Care and let them know when and where will be flying, so that a TSA supervisor can accompany us through security all the way to the gate. This way we skip the regular line and go through metal detector. Well, we'd go through metal detector anyway since my son is only 8. The TSA can still hassle us if we try to bring juice boxes that are larger than 100ml — in that case they either will ask to open and test the juice or pat down one of the adults.