I think you're misunderstanding how the stamina works. It's really only a bother in the very early portions of the game when you're just getting started, a few days at most. This game is generous about dolling out new characters while playing the campaign and coins are easy enough to earn that you can always be buying more. The timers in this game are way friendlier than in many other games, and in fact I don't even think they're implemented as a way to push towards IAP. If they weren't there, you'd just level up 3 characters to the max and use solely them for the entire game. It would be pretty dumb. The fact that they have a cooldown means you're constantly mixing and matching characters and trying to use different teams. It forces you to explore the full roster, and not just cheese through with a couple of powered up fighters. I actually think it's more of a gameplay mechanic than a freemium mechanic. I've been playing Injustice for a long, long time and it's at the point now that if I sit down and try to play continuously by burning through every character's energy in a row, by the time I get to the end of the roster the characters that I began with are already fully refilled. This means I will never, ever be forced to stop playing because of the energy bars. Honestly I don't think I could play much more than a couple hours straight of Injustice anyway! All this is just a long-winded way of saying don't let the stamina bars scare you or your son off. It would be nice if there was a way to avoid this slow early-game progression, but the game opens up so significantly after it that it would be a shame if he skipped out on a game he otherwise enjoys just because of it.