We don't own one yet, but I have read good things about the EZ Cruiser Lite and the Airhawk. I will be following this thread to see other comments.
We went with the EZ Lite Cruiser for our 8 year old. We had to modify it because he is a little small for it but would be perfect for a 12 year old. It's about 60 pounds and can be folded up and put in trunk.