Good plan, and I think you have your liability bases sufficiently covered. A church group on a good-will outing should be very low liabililty risk anyway.
Some will be intimidated by the 7-8 mile length especially if any hills are involved, so I encourage you to be more inclusive by allowing some participants the option of a shorter alternative ride, say 2-3 gentle and slow miles. For this group emphasize the pleasure of riding, the exercise can be progressive.