You just need enough battery to get the four days done and recharge them when you get home with a simple 10 amp charger cost maybe $50.
Usual rule is one battery gets used per day. Or you can recharge the two batts half way through. Get the WFCO running and take the gen and your 10 amp charger just in case, and do a small recharge every day with them when convenient not to interfere with camping fun.
make sure the batts get fully recharged as soon as possible after getting home.
Do have a voltmeter display somewhere. BTW the range hood lights monitor is a voltmeter. You can tell as it drops through green to yellow to red how that is going close enough to know if you need a recharge.
Don't forget it will drop a colour when you run something and then bounce back up after that stops running (loaded voltage effect) When it doesn't bounce back up and stays at that colour, now you are there at that level.
Tim Horton's eh? :)