Cole, that's cool that they took you up for a tour ride. When you get a little more comfortable with the pilot you can ask him to get lower and stay steady abeam a race vehicle.
I found a good way to get sound is with an external lapel mic, or you could use an ear bud with mic, and stuff 1 or both in the ear cup of your headset. It will block out the rotor noise and record the intercom. Also the suction cup mount for GoPro holds fairly steady when mounted on the overhead glass or door window, and you could still pan with it if not tightened down fully.
How many helicopters are there on the lakebed?