Thanks to all for your suggestions.. so I did it this morning at 9:30 am.
I did have trouble holding my line. Either I was too far over to the right or too far to the left of the white line but my friend did a great job of pushing me (literally) over the hills while I brayed like a donkey from the exertion. Eleven people turned up for the ride and all apparently had the honor of being pushed over the hills when they first started the ride. Biggest suggestion from all was to keep doing the ride and it will get easier. Got a nice round of applause for completing my 17 miles too. I'm not as nervous as I thought I would be about the cars, just holding the line. ALL in all GREAT RIDE! I don't want to see another hill right now, but definetely worth the experience.

Now to control that breathing so people won't think Shrek the donkey is in their neighborhood.