Outdoor shower/water day for kids.Could easily be made with hollow box uprights, run the water tube through one and the top hollow box with a PVC tube that you drill holes in for the water to run out. Faux paint it to look like copper, really pretty easy.
S'mores bar - roast your own s'mores. What an awesome wedding reception idea! Would be so much fun for kids- although wouldn't it be more fun (if you have a small wedding) to have a Campfire outside and roast s'mores