K.
Water balloon grenades... Make a "fort" out of a cardboard box that the kids could paint green and cover with leaves and/or branches...Hide and go seek with a "take the found people as POW's" twist to it...a scavenger hunt with army-type clues and prizes...relay races set up like a boot camp (climbing, crawling, rolling under a table, hiding)...a game like "telephone" where the kids relay "secret strategic messages"...that's all I can think of, hope this helps! K.