Good advice by all! As mentioned, you don't want to deeply discharge your new batteries, you will take years off the life of them. If your daily use is, say 100AH, it would be wise to use your tow vehicle and a set of jumper cables to get some charge back into them on a daily basis.
A small solar setup would be ideal for the way you camp and, if you're away from the rig when it's stored, it will keep your batteries at full charge with no work on your part. Also, think about how much cred you could get with the FIL by not using a generator.
Your onboard conveter will work fine for restoring charge to the batteries but you want to make sure it has a low enough float voltage so that the batteries aren't constantly charging at 13.5 or so. Your Schumacher charger may fit the bill, also, but float voltage should be ascertained, just like the converter's output voltage.
Harbor Freight sells cheap multimeters that fit the purpose for battery measurement. They are not that durable but are fairly accurate for voltage measurement. If your Schumacher charger is discovered to be not adequate, HF also sells an inexpensive multi-voltage charger that gets good reviews.
Good luck with the new batteries, appreciate your input to the "Sam's vs Costco" thread.
