Whenever we have company over to swim (kids), I always set out some watermelon. You can do 1/4 slice wedges if you want. But since it is a small group of very close friends and they're all kids and have been in the pool swimming non-stop and are about to hop right back in, I usually just cut it up into cubes and put it out in a couple of bowls. They use their hands, or if you trust them enough, you can put out toothpicks. Same thing with fresh pineapple. You could make skewers if you want, but be careful if your 6 year old group includes more than 1 boy. You will likely end up with sword fights, lol.
I also set out a big bowl of pretzels, either sticks or the smaller size regular kind. They are always GONE by the time the guests leave. --it's easy, and no mess. Just dump the bag out in a plastic serving bowl.