When we got married we didn't bother having different wedding cakes for different food intolerances. Luckily we found a vegan gluten free wedding cake that was delicious enough for everyone.
In fact we ended up having all the food vegan and most of it wheat free - we found vegan caviar, vegan champagne, vegan smoked salmon pate and a dairy free chocolate fountain using belgium dark chocolate.
Everybody loved the wedding cake and didn't realise it was wheat free or vegan. We got the wedding cake from a company called zedz Foods www.zedzfoods.co.uk who are based in Wales but do mail order and are available in some shops.