The kids were looking for something to do so I pulled out the t-shirts and paint I bought them to make some splatter paint 4th of July art. You basically lay out a white t-shirt and, using a paintbrush, throw paint everywhere. It's quite fun, but messy. It's takes some serious slinging, so it's a bit easier if you stand up above the shirt and give yourself a bit of room.
Of course I got a little video of the painting action, and yes, there is now paint all over the picnic table. They were both a mess once it was all said and done, but they turned out pretty good!