One thing to consider is that there are two styles of USB outlet -- auxiliaries to 120v outlets, and outlets that run directly off 12v circuits. If you need to charge phones but will be spending a lot of time without shore power, make sure you have enough of the latter. If you want to get fancy, you can tap your accessory circuit and install one
in the wall [LINK], or you can just get a dongle like
this one [LINK] and plug it in behind the TV.
(I don't necessarily recommend either of these brands, I just used them as examples.)
Most if not all of your lights are already 12V anyway, so no problem there.
The batteries are an entirely separate problem. If you think they're damaged or aged out, replace them regardless.