Hawks channel is very easy to navigate, there are not many things to worry about. It's a fairly straight forward sail down and with the right winds it's a cakewalk. I don't know about staying the night on those mooring balls though, it would probably be a lumpy night.
Marathon has one of the best protected harbors around, Boot Key is a great place. The town isn't exciting, it's far more laid back then bigger areas such as Key West
, as a matter of fact it's pretty much shut down around 9pm. Of course this is one of the things I like about it, I didn't want to live somewhere fast paced. You won't find a more helpful community anywhere else though, people will literally give you the shirt of their back.
Goodluck and if you stop by Boot Key, say hello!