Jarrod, I don't think Mywifesirrational is trying to say that the neck brace didn't serve its purpose in the case of your crash and that god intervened.
He is saying there is no scientific data to suggest that neck braces are as effective as their marketing suggests, or the anecdotal evidence provided by users of neck braces suggests. Well, That he is aware of anyway. But, from previous discussions I have read, I believe this is this is somewhat his field of expertise.
Thats not to say they don't work at all. There are an unbelievable number of variables that determine the outcome of a mountain bike crash. it is impossible to pinpoint how effective a neck brace would be in an actual crash unless you can isolate all of the other variables. Thats where a study would come in. as yet, it seems there aren't any.
Back to the OP.
BDL, I think if you could get your kid to wearing kneepads, and try and convince him to use some slimmer, under jersey armour. you would be on a winner. Just show him Ratboy, he wears an MX roost guard in the WC races.. and the kids love him.. lol