Dan, as you well know the best thing is to get them out shooting - a small dose of that trumps any video game on earth. I suspect you've got the hardware side of that covered well.
Then you might consider a Crockett kit from Traditions:
https://www.traditionsfirearms.com/product/Crockett-Rifle-Kit-.32-cal-percussion We have one of those that I bought for my son (finished, 2nd hand) and it fed his interest well.
He's in to that sort of thing, tho. He prefers a longbow over any other choice and if you invited him squirrel hunting tomorrow he'd show up with his .32.
BTW, he was a video gaming machine, too. Until given an outdoor or shooting alternative!
