First off you can't use plugins in LAN, and there are ways to reset without the use of plugins with commandblocks. Here's how the auto reset should work:
Create a scoreboard objective Start as a dummy. When the kids press a button to enter the game which is how this will be setup, then have a block set the score of Start to -1. Another commandblock should be placed with a clock connected to it testforing everyone for the score of -1, if so then a comparator that turns a redstone torch off that' connected to a bunch of commandblocks that reset the game using /setblock and stuff.
Wheb out of the game use commandblocks automatically when it ends to put them in a team Player, so that when its testforing @a to all have a score of -1 it can testfor the specific team. Also put some commandblocks to detect a win condition to be met connected to a clock, and if so reset everyone's Start score.
I typed all this in assuming you had scoreboard and commandblock knowledge.
If you want a game to play with your kids with the similar autoreset system checkout my Slender game.
