My son had 5 friends come and join. We pretty much followed the same routine as my daughter's princess party. The children arrived, they played for a while, then we made our craft--race cars. We then went outside for a race with pedal cars, came back in had water ice and cake, and we were good to go.
For decorations I purchased a race theme tablecloth, plates and napkins. I also bought strips of hanging racing flags for our "racing area" outside.
The children arrived and played a while, then we made our race car crafts. For these I had gone to a local grocery store and got some medium sized cardboard boxes which I then cut all the flaps off of. Then I went to a craft store and got paint, some large letters, and black construction paper. Each child got a box and they were allowed to paint it as they wished. We had spread newspaper all over the floor in the basement so they could spread out and paint, and I didn't worry about paint getting everywhere. After the boxes were painted I gave each child the letters to their name and they glued on the letters and then 4 wheels I had cut out of the construction paper. Then they could "climb" inside and take off.
We followed the craft by going outside to have pedal car races. Our family had one racing pedal car and I was lucky enough that a neighbor had another pedal car. We placed orange cones in a row to make two straight courses. The children raced two at a time. They got in their cars, the flag man waved his flag and they were off. We didn't have winners, or losers--just racers.
After everyone got their turn we went back in. My son had wanted water ice for his summer party, and we had a beautiful race car cake made by my sister-in-law. Everyone enjoyed their goodies.
I had given each child a goodie bag with a small car, Hot Wheel gummies, and bubbles(that's all I can remember, there may have been something else in there). It was a fun party and kept everyone very busy.