If you want to get good liability INS for leading rides and events where you instruct the public on safe riding, it is worth looking into the LAB's certification.  They include coverage if someone is hurt on your ride, and if they are hurt later, and claim that you "told them to ride in the middle of the lane" .  There are some paperwork hoops to jump, but you should be tracking participants anyway, and it is pretty excellent coverage for $25/year (after passing a $500 certification seminar).