I believe that the MVP benefits only apply to travelers on the same reservation. The cost to transfer their miles to your account would surely exceed the cost of checking a few bags.

I don't know the official policy on this, but when I've traveled with kids on separate reservations from mine, I have had success calling the MVP line and asking nicely for seats next to me in the MVP seat area. (I wasn't asking for exit row.).

Be sure to use the "link reservation" feature on the AS website so that AS knows you are all traveling together on separate reservations.