We tried GF with my daughter and had limited effect. Recently she was allergy tested and found to be allergic to Corn, Dairy, and Peanuts. The fact that the corn and dairy rated higher than the peanuts made her doctor suspicious of the test, so on a hunch he had us cut out corn but leave dairy (she's actually had a reaction to peanuts so we're not going to play in that yard).
Anyway, her behavior has greatly improved, the trick is actually avoiding corn completely. Its in EVERYTHING!
As far as the folks. We've had trouble with both sides accepting her diagnosis. They just kept saying we were bad parents and not strict enough. They are finally starting to come around, a meeting with my daughter's psychologist helped alot. Both sides have quit denying her dx. My folks are trying hard to understand, but this is totally different from anything they've ever known. So we give them credit for trying hard and try not to dump "everything-we-know-about-AS" on them at once. The in-laws are a different story. They were kind of accomodating when she was the only grandchild, but now they have another 1 and a third on the way so they're sort of acting like they don't want to be bothered with a "defective" child. Oh well, their loss.