Fill balloons (white or colored) with glow sticks for an awesome party decoration, or just as a fun past time for the kids. After your balloons are half filled with air, carefully insert a glow stick or two, and then finish blowing them up and tying them off. These would be cool hung upside down from the ceiling!
bawww this makes me so happy! how fun would it be to have a bucket of water balloons and squirt guns waiting... in fact, why not make it a whole "welcome to summer" BBQ (glow sticks, star gazing, lightning-bug-catching... sounds like a summer night to me!)