Hey Leasha, sorry i cant help you re personal experience, but I do remember a thread around here somewhere about kids wearing helmets (I think it was to correct "flat spots" from sleeping) I seem to recall that there were quite a few replys.
If I knew how to do a thread search I would go look for you. Maybe you will have more luck than me.
Good luck with lil Jaz, from memory, the kids coped with it fine and it wasnt for long