Here's a fun game of toss that your kids will love to play at the beach.
Place the target rock or stick in an open area of sand away from other beachgoers. Scratch a line in the sand 8 to 12 feet away from it. Players take turns standing behind the line and trying to toss a stone as close to the target as possible.
Once all the stones are tossed, check to see which came closest. (Bouncing off the target doesn't matter; what matters is where your stone lands.) You can play as individuals or teams and score the rounds separately or accumulate points toward a set goal. After several rounds, try moving the line farther from the target.