As I've said before, if you're into the realism of a game, allow the players a chance to obtain tactical advantage and then simulate the events with markers (game pieces, figurines, whatever) and any kind of grid. The players may be outnumbered, but if they use strategy to their advantage, they can usually win. I go overboard with small tape measures, 1 cm = 1m, usually. For long distance use 1 cm = 2m.