There will be a HUGE difference in abilities. Expect riders all over the course. Try a neutral start with a ride leader in the group, and have him/her ride with them a lap or more, then let them loose. It would let some women ride with the group instead of being OTB at the start line.
Cornering will be a biggie. I had to yell at someone on Monday not to try to pass on the inside of a corner.
How to get lapped will be a biggie there too. A group lapping you will have the right of way, so to speak.