My son has a couple of BB guns...
All my children started shooting .22 pistols when they were 5, the age of your grandson....
My oldest daughter, now 20, competed on the US Air Force Academy Rifle team last year, NCAA.
This year she competed on the combat pistol team, non-NCAA.
My middle daughter (16 years old) had me take her and her friends to the pistol range for her "Sweet Sixteen" birthday party....she out-shot her boyfriend, snicker........
My 14 year old son....he's a natural...very focused and relaxed when shooting. He would like to go to Annapolis and become a Seal Team sniper....OBTW, he also wants to be a Catholic Priest.....LOL...We told him he could shoot his target and administer last rites....
Great family! I have a son who want to be a priest, too. How that will square with being a Confederate re-enactor, I'm not sure ...
No reason he can't do both. The "normal" order would be SEALs first, but "semiary first" would also work.