Thanks for the replies everyone! They have given me a lot to think about. The short answer sounds like get both a Corn and a BP eventually, but it brings me full circle as to which to get first...
My new approach is going to be to say we're going to go get a BP "together" which basically means that it's going to be my snake first with some assistance from my son. If he really takes to it, then in 6-12 months we can go back to Repticon and get him "his own" Corn which may not be a hatchling. Best case scenario, he likes both of them and takes over most of the upkeep as his gets older. Most likely scenario, I end up with a BP of my own (or he loves the BP and I end up with a Corn for myself). Worst case scenario, I end up owning both a BP and a Corn which really doesn't sound too terrible.