This is what we did for my daughter's 5th birthday. She invited boys as well as girls, and the party was inside.
Including my daughter, there were 12 children, all in kindergarten. As the children arrived at noon, I lead them in Simon Says. No one had to sit down; we would just say, "Ooooh'" when someone goofed up. Then the children spread out a tablecloth on the floor and were served chicken nuggets. They had juice in sippy cups that I had bought and put their first initial on using a paint marker. I let the children identify which one belonged to them. They got to take the cups home with them. After lunch we played the traditional Pin the Tail on the Donkey. Then the children wandered into the family room and played with our toys for awhile. Everybody was rounded up and were brought back into the living room for Scooby Doo Paw Relay Races. The children had to wear a Scooby Doo paw that I had made out of a cereal box laid flat with tan fur glued on it and a hole cut in it (this was a modified version of the Dinosaur foot described in Family Fun magazine). The children had to carry a dog biscuit on a teaspoon while wearing one Scooby Doo paw. It was a lot of fun! Then the children played Duck, Duck, Goose for a little while. The last fun activity was decorating cupcakes. The children laid out the tablecloth again. Each child was given a plain cupcake and could decorate it with chocolate frosting, vanilla frosting, sprinkles, nonpareils, and tiny sugar candies. Most kids used every thing available. Then my daughter opened the presents and the kids went home. It was all over in 2 hours!