As an officer with my local H.O.G. chapter, I've actually had a bit of training on this and you probably won't like my advice:
You still expose yourself to a big liability issue. The fact is, Poker Runs are lots of fun but never make money if they're done in a manner that protects the organizer. Many charities will decline to have a poker run done using their name because of potential liability.
You have two choices if you insist on a riding based fund raiser:
1. Do the run without insurance, and pray nothing happens. You'll make a few bucks.
2. Do the run with insurance and make little or no money.
It sucks and it's not fair and the lawyers will tell you that they're just advocates, but the fact is that they've insured that no laws get made or passed to protect someone trying to do something for charity. The AMA and H.O.G. and some other organizations have insurance to cover official rides but even then there's a insurance fee when you open them to the public. And it's almost always is as much as you make off the ride. And if the weather turns bad, you could end up owing more then you make.
Pass a can and then go for a ride. Tell people they're welcome to follow you if they want. It's up to them.
Ride Safe,
J-Carr