My car has been dirty for quite some time. Last weekend we decided to finally clean it and our VW. We got the materials like soap, wash rags, and a bucket, and headed outside. The kids got to "help" by playing with the water and splashing it on everyone. It was pretty nice to have a family activity while doing chores.
The kids got a little tired of washing cars and went off to play on their bikes, but we had parked right next to the concrete loop they like to play on so it wasn't a big deal. Every once in awhile they would come back to play with some bubbles, get squirted, or what not. Only took about 2 hours too.