I install a punt, even with kids as young as 9. This past season, it was valuable to us when we put other teams into slaughter. If our second offense was on the field, we'd use 4th down to boot the ball as deeply as possible to give our second defense more space to defend.
I think whether you utilize a punt or not is contingent on how good your team is. Years ago, with the 1-7 team I coached, I had a punt installed and we punted all of the time and really I don't think it did anything for us in the games where we were really outmatched. The close games where our defense was shutting down their offense and vice versa, the punt was useful. But if you're against THAT team that manages to land the blocks they need and run for a TD on what seems like every play, a punt is going to do nothing for you.
Where I want a punt installed is...it's been my experience with little kids that you can pretty well count on them to screw up at least 2 series a game. Say you receive the opening kickoff and somehow the ball has a nice roll, skirts between your deepest backs and comes to a rest somewhere around the 20 yard line. The kids have a series of brain farts, bad snaps, bad tosses, penalties, whatever that puts you back on the 10 or 15 and it's 4th down. Do you roll the dice or do you boot the ball?
I boot the ball. I boot it for a couple of reasons. The further the other team needs to move the ball, that's more opportunities for us to take the ball from them. It's more opportunities for them to mess up. But again, if they come out of the gate and immediately run for a touchdown, it's going to be a long day for us regardless of having a punt.