My experience is the person who's going to service your motor, lower unit, etc won't be the same person you want detailing your boat. So, if it were me setting this up as a new company and I wanted to offer all of the above then we are talking about more than one person which may be tough to do out of the gates for someone.
For me personally, I would just want the mobile detailing service. I'd want them to clean every inch of the boat from bow to stern. This would include cleaning carpet, all compartments, ice chest, glove box, etc, etc. I would want the carpets cleaned and the boat washed and lightly waxed.
I would think with this service coming to me to do it, I would pay $250-$300 and would rather just have the tip build into the price and if someone just knocks the cover off the ball, I'd tip some extra.