Hi B.,
Tug of war? Can get a little rough, so consider the kids you are working with.
A variation on what Ramona P said--
Bug in a Jug: For each team, get one plastic gallon milk/juice jug, one one-cup measuring cup, a plastic bug ("Creepy Crawler" type) and a bucket of water to dip water out of. Put bucket of water by front of team line, put jug 50 ft away, with plastic bug inside. First person from each team fills the cup with water, runs/walks to the empty milk jug and dumps water into jug. Runs back to team and gives cup to next person, who repeats. Eventually the bug will rise to top of jug (maybe a good idea to test whether the bugs float before you bring them to the game site!) First team who can pull their bug out of their jug wins. No, it is not allowed to dump your jug to get your bug!!!
You can vary the size of dipping container (one cup, half cup, pint, tablespoon-lol--LONG game there!), distance to jug, and the means by which kids get themselves to jug--e.g., walk, run, hop, 3-legged crawl, skip etc.
If being wet is not a problem, you can play a pass-the-sponge game. For each team you need two buckets, one full of water, one empty, and a sponge. Put full bucket in front of team line, empty bucket in back. First person puts sponge in water til it is wet, then passes it over his/her head to next person, who passes it over his/her head, etc trying not to squeeze too much out. Last person squeezes sponge into empty bucket, runs to front of line (everybody scoots back to fit), and dips sponge in til it's wet, and passes back to next person etc. Object of game is to get the most water in back bucket. You can play until water in front bucket is gone, or once through the line of having everyone be the "starter", or 5 minutes, or..... and then compare water level in the buckets.
You could also have them pass the sponge under their chin to next person--they get really wet that way!
If you don't want them to get wet, pass an orange or rubber ball or softball or kooshball (all same for each team) under their chins. First team to get it from front of line to back is winner.
Make paper airplanes and try to fly them into a circle laid out on grass.
You could do some brain games too for those who can read--boggle, for instance. Or have each team form their bodies to make letters and make a word (Think"YMCA" by the Village People here). Or have a bag/box full of slips of paper with nouns on them, the funnier the better (e.g. elephant, ferris wheel, sauerkraut, mouse, etc). Pull four out at random and have each team make up a poem (or story) using them.
Or get a book of Mad-libs and do those just for fun.
HAve fun!
K. Z.