I don't think you can rent a helmet if you are scheduled to run a full day as a driver. Chin will rent a helmet to a person that wants to do ride alongs. I believe they are $20.00.
I use the Cinemount in my car. I also use my IO port camera mount, it attaches to the cage.
IO Port Racing Supplies: I/O Port Video Camera Mount
Chin Motorsports is holding a drivers event on Nov 11th and 12th at Sebring. They always welcome people to come check out the event and do some ride alongs.