When a travel season ends there is this dead space before tryouts and that's usually where something like 3 on 3 is great. Anytime you can pack the kids in close they start to read and react quickly learning how to transition quickly back and forth from defense to offense.
There shouldn't be much coaching here; just kids playing and allowing the game to teach the game. You'll see way more touches and shots and if they want the puck, they learn to get open and be a target. No way you get this many opportunities in a full ice game. What's nice about keeping the coaching out is that the kids can just have fun and be creative. Having balanced teams, however, is important.
In the off-season, let them do something else. You are always going to find the kid who just can't get enough but most just want a break and they will come back better for it.