If all else fails, use the Blues Brothers gambit. “If you hassle us, we will bring our kids back here three times a day until we are your only customers. If you let us finish our meal in (relative) peace, when we walk out the door, you will never see us again.
Having been a participant in numerous outings with my nephew, I only wish we had known about that little piece of advice. Dwight actually sent me a link to another post from a high order autistic teen, but I’m saving that one for tomorrow.