How long your battery (or batteries) is going to last is all about how you use them. We have a 21 foot travel trailer, and the "standard" 12 volt deep cycle battery (which looks like a regular car battery) can last over 5 days. This is with using battery camping lanterns in the camper, not using any camper lights unless necessary (midnight bathroom trips, lol), not using microwave oven, and just watching any and all power usage of the trailer.
If you are thinking of long term boondocking, then research solar power. A properly setup system is basically something you don't even have to think about, it just works - and it is quiet!
For just one big trip, I would lean towards a generator, especially Honda. Heck, why not get a 3,000 watt Honda that can run your air conditioner and microwave? It is impressive how quiet they are, and most times you won't have to have it running constantly.