With the warm weather soon approaching, you can always have a party outside.
You can set up a wading pool for the kids to play around in. Squirt guns or bottles of bubbles can entertain for hours.
If the party is in the early evening, string holiday lights around the fence or door to make the day more festive.
If you are going to have a large crowd, you can always have a party at the park and have everyone bring sports equipment, balls, and frisbees. And the kids can play on the playground equipment along, too.
Have you ever had a party outside? Any hints?