Hi RedRiding. welcome to the shiny world of GF (pain in the bum, isn't it?!?!!!)
i can't offer tips to stop the complaining i'm afraid, DD has been amazing on that front - she clearly remembers feeling shit all the time, so all i have to say is you can't have it because it's not gluten-free, and she accepts it (we've progressed from "bad for my tummy" to "gooten-feee") 
we eat out a lot too, and i work in the restaurant business, so that has been a big pain. i'm never 100% sure i believe them when the waiter vaguely replies "um yeah, it's gluten free", and i've marched into the kitchen on a couple of occasions to speak to the chef! Carluccio's are very good, they whip out a whole secret GF menu if you ask which has dozens of dishes on, including pastas and ice cream! I generally have a range of GF products in the nappy bag just in case, although we got caught out on holiday the other week when i didn't have any GF bread/crackers and all i could give DD for lunch was a piece of cheese and slice of ham and a yoghurt :(
at home we rely quite heavily on GF replacement products (she is getting better, but is still picky and most of her diet is based on pasta/rice/chips/toasties etc). i have about 5 local shops that i go to for the variety. the only thing i have yet to track down is croissants :(
DD has ended up eating more chocolate and sweet things in the last 3 months than the rest of her life, because of me over-compensating every time we are somewhere that she can't have what's on offer! We've got our first post-diagnosis kids party to go to tomorrow (which i'm dreading a bit), so i'll be armed with a variety of cakes/biscuits/snacks/GF squash and hot chocolate!!!
it's very irritating how much stuff has gluten in it, quite uneccessarily IMO (hot chocolate! stock cubes! cornflakes!!!). we've tripped up a few times, but i think that's inevitable.
and re point 1 - tell them all to F OFF!!!!! i can't stand that look that says "oh, your one of those neurotic mothers", as if gluten-free was some kind of fad diet!!!!!
don't worry, it'll become routine soon
:)