I have a killer recipe for a flourless chocolate cake that fits the bill except for
being egg free.  I am not at home for the next two weeks so i can't do an
experiment for you to see if it works with flax seed gel.

if you don't have any luck on this list you may want to ask this same question on
the GFCF Recipes list on Yahoo groups.  Many of the women n that list are
cooking for children who have the same restrictions as your son.

Good luck and happy birthday to your son.

Shez