J.C.
Why not have a sports party? You can actually rent out baseball, football and soccer fields in Mesa for very little money. If you go on the City of Mesa website they have the prices for the fields under the Parks and Recreation section. Since his birthday is in May it will be starting to get warm, but you can have them play baseball with water balloons and put up shade canopies. You could even rent a shaved ice machine and have snow cones after the game. You can have Cracker Jacks, peanuts and popcorn in bowls on a table or also rent a popcorn machine and serve freshly popped popcorn. Fill ice chests with water bottles, gatorades, etc. and have pizza delivered to the park. Decorate with his favorite team colors or if you are picking a specific sport such as soccer, decorate in black and white. For goody bags, fill empty water bottles with candy, sport tatoos, whistles, etc. and write each child's name on the bottle with a paint marker. If you go to orientaltrading.com you can buy this stuff in bulk and spend a lot less. If you have more money to spend divide the guests into teams and have different colored shirts for each team (the same colors of the party?) You could put the number "6" on the back of the shirts or put each child's name, but that can get really pricey. Just some thoughts, just let me know if you need more ideas!