I don't really understand charity "events". It is a funny concept to me. I sign up to participate in an event I am interested in participating in (a bike ride, run, etc.). In order to participate, I am required to ask my friends to give money to a cause. If they do so, I get to participate in an event that is worth more than the (possibly) smallish fee that I paid to register. So, essentially, I am supposed to ask my friends and family to pay money so I can go have a good time. They, in turn, may feel guilty enough to give to the cause so as to not feel like a selfish person.
So when it comes down to it, I am asking my friends and family to pay for my good time doing one of my hobbies. Sounds like a scam to me. Especially when one considers just how much of the money that my friends are giving goes towards actually helping the people or cause that the "event" is sponsoring. I have less issue with events where I pay an entry fee that supposedly supports a cause. At least there I am paying money and I am getting the benefit of the event organization. But why should I ask my friends to pay for me to enjoy such an activity?
Jack and Back sounds like a fun bike trip. But I have no interest in asking my friends to donate money so I can ride my bike to Jack Daniel's and drink whiskey to my hearts content. I also have no interest in paying $350 myself to be able to do that ride. I think MS might be a worthy cause (I have no info on the cause and its organization), but there are many other worthy causes. I think I would prefer to pick one that hits closer to home. And I think that I would prefer my friends and family do the same.