For my son's 8th birthday in August, we had a backyard water party. This party can be held completely outside if you wish. The invitations were bought and printed on my computer. Any water related card will do and can even be completely made on the computer. First, as the guests arrived, we played water balloon baseball. When my husband pitched the balloons and the boys hit them, they exploded water all over them. You can buy biodegradable water balloons so you don't have to clean up the mess. Then, we did a water relay through the backyard. First they ran past parents spraying them with water guns, then slide across a slip-n-slide. Then they had to eat a powdered donut that was tied to our swing set. We removed the swings and tied the donuts up pretty high and made them hold their hands behind their backs. Once they ate the donut, they climbed up the rock wall on our playground and slid down the slide into a kiddie pool of ice water. We tried to fill the kiddie pool with gelatin and ice water, but it didn't really work. Ice water will do just fine. We didn't tell any of the kids including the birthday boy that it was ice water. Once they were down the slide they received a huge water gun and proceeded to have a water fight. We had more water balloons for the end of the relay. The parents got involved in it too. The water gun was their gift to take home. I bought them on clearance the summer before. The garage was decorated with balloons and streamers so we had the boys dry off and we had an ice cream cake decorated with balloons and splashes of water and we opened presents in there. Since most of the parents stayed for the party, we had snacks for them inside the house. It was the best party we've ever had and some of our friends are still talking about it 3 years later.