My son was just diagnosed with CELIACS Disease any helpful? advice?

My son is 6 and i am just looking for any helpful tips. I am going to a dietitian tomorrow so any tips for that appointment would also be awesome. Trenton is very active and has suffered for years, due to no diagnosis. no that we have an answer it is kind of scary but we r strong and will be for him. So i am reaching out to any kind of knowledgeable people and i am hoping for great advice. Thanks a ton!!!