I've installed these:
https://www.amazon.com/dp/B00ZOG6TBE2.1A 5V output from each port. Mount 2 and charge 8 devices. The real load of 2.1A @5V is 11 watts which is only 1A @ 12V. Most 12V circuits are 10A or 15A, plenty of room for all your toys!
Put them where there is already unswitched 12V and check the fuse for that circuit. Mine are next to the radio and the bedroom lights. Near your control panel is a likely spot also.
On shore power just use whatever you use at home, or install things like this for your 120V receptacles.
https://www.amazon.com/dp/B013QP0OWY