We started the haircut in Andrew's lap but Peter was extremely wiggly so we strapped him into the highchair and even though he was still wiggly he couldn't lay down on the ground which really hinders the haircutting process.
I cut a lock of hair from the top of his head for his baby book (one day I'll start & finish it) and then we just used the trimmer we have. I think this means that we'll need to get a real haircutting kit soon. Maybe his hair will start to grow faster now that we've cut it. Who knows.
Here are some before, during and after pictures.