I agree don't make ferry reservations. They will not guarantee you a spot if the boat is sold out as it will be first come first served. Buy your ticket on arrival for the next departure.

You outbound ferry departure will leave you plenty of time to get a drink at the bar uptop the ferry the terminal. On the return I would look for an earlier ferry. Too many things could wrong and the two hour window you are allowing is not enough if there are any delays.

At the Moorings the charter briefing and boat checkout are two different things. If you need the charter briefing do it online as suggested. The boat checkout is done the morning you depart the dock. This will include a review of all boat systems and an inventory of equipment. If you are not familiar with the particular boat you will be on take your time with the checkout. Even if you push it an 11 am departure is probably the earliest you will get off the dock. When you are ready for the checkout ask for it at the customer service desk. You may have to be persistent as the dock staff work at island pace.