i have coeliac disease and am aware that restrictive diets shouldn't be adopted for children unless under medical supervision.
however, saying that, I'm sure you have a good reason for wanting to try it.
Coeliac UKs website is good, but i'm not sure what you can access as a non member.
breakfast is a pig of a meal to get right; the choices for GF cereals are limited, although my favourite is Nature's Path Mesa sunrise flakes. there are a couple of kiddy ones though; you can buy them in Sainsbury's.
Most of the supermarket ranges have a freefrom section now. english muffins are good, the seeded rolls passable, but most of the bread is gagging awful. Tesco do a ciabatta style which is the best I've tried so far.
the best pasta I've found is the Salute brand which is sold in Sainsbury's.
and watch out for labelling. some things say contain wheat even when it is an approved ingredient which shouldn't cause any problems (like glucose syrup from wheat)
coeliac uk should have a list somewhere showing which are OK.
and be prepared for your usual shop to take at least three times longer until you get used to what you can and can't buy, but check labels regularly as recipes are often changed.