FWIW, I would let the youngster be a part of the selection process.
There are so many fine tube-fed, and mag fed semis out there, all I can say
is be sure you get a good brand name you trust.
If the 12 Y.O. involved prefers accuracy to speed, there are few nice
tube-fed bolties, also. I would be more concerned about proper trigger pull
(a little long would be better, to allow for future growth) than specific
brand names. YMMV, best of luck.