You gotta lotta issues here buddy.
Okay first of all, it would be better to use just one big bank, than to split it into two smaller banks. The reason is this thing called the Peukert Effect. Basically, the larger the load is, the faster the batteries go dead.
Now that sounds like perfect sense, but it doesn't mean exactly what it sounds like. Let's say you've got a 10a load on a 100a battery. Okay, that battery can run that load for 10 hours. But say you drop the load to a 5a load - the battery will run that load for *more than* 20 hours. Double the load to 20a, and the battery will run it for *less than* 5 hours. It's a sliding scale.
The way that works out, is that if you double the battery bank size, but don't double the load, you'll get *more than* double the run-time out of the battery bank.
Your next issue is charging. You don't have to disconnect batteries from load while charging IF you have a big enough charger. Say you have a 50 amp charger, and 20a of loads running. Well, the charger will supply those 20a of loads and still put 30a into the batteries.
Now, doing a little quickie net research, from your description, I'm guessing you got the Crown CR-260 batteries. The Crown manual says:
"Crown Battery recommends electronically controlled automatic chargers that are programmed to deliver a high constant current rate of 12 to 18 amperes per 100 ampere-hours (20 Hour Rating) of battery capacity."
https://www.crownbattery.com/en/wp-content/uploads/2013/09/Deep-Cycle-Product-Support-Broch.pdf
Which means first of all that no, you can't use a standard benchtop automotive charger - those are constant voltage, and you need one that can do constant current. Oh, the automotive charger will get the job done eventually, but not good enough, not fast enough.
Battery companies always specify the size charger (amount of current) based on the capacity of the battery or bank. They usually say something like C (in this case, that means "battery capacity" - not "the speed of light"
) divided by 4 or C/4. In Crown's case, they are recommending between C/8 and C/5. Let's say you rig two of those 6v 260ah batteries in series to get 12v. Now you have a 12v 260ah battery. Well the minimum charger you need is going to be C/8 or 260/8 = 32a. You'd be a LOT better off going to the max though. That would be 260/5 = 52a. So you need AT LEAST a 30a CONSTANT CURRENT charger, but you'd be better off with a 50a.
Double that if you rig all 4 into a single bank.
If you DON'T follow the minimum recommendations, you WILL shorten your batteries' life.
If you are going to charge at the same you are running loads, then you need to add the loads as well, so say you need a minimum 30a charger and you've got 20a of loads running while you are charging - now you need a 50a charger just to meet the battery's minimum charging requirements.
The next question is will your generator run that charger? Dunno what you've got. For example, a Honda eu2000i is rated for 1600w continuous load.
1600w / 120v = 13a.
An Iota DLS-55 will pull just over 13a on the 120v side under full load. So yea, a phased plasma rifle...er...I mean...a generator <Arnold Terminator voice> "in the 2000 watt range" will supply a 50a charger.
So what sort of charger are you going to need? Computer controlled 3-stage which can do a constant current bulk stage (gets the battery to around 80% charger as quick as possible) and then can do a constant voltage absorb stage (to push it up that last 20% - which will take like 8 hours) and then drops to a float or maintenance stage).
I would recommend the Iota with IQ/4 brain module. The reason is, that while Crown recommends taking the battery to 14.5v, the Iota with IQ/4 will take it up to 14.8v. This will A) get the battery charged a little quicker, and B) get a little more charge into the battery. The down side is that you'll use a bit more water so will need to keep an eye on water levels. But with 500 bucks worth of batteries, you better be keeping an eye on them anyway if you want them to live as long as possible.
I would say go with a DLS-75 in order to supply loads and still get the full 50a into the batteries:
http://www.iotaengineering.com/dls75.htm
But the 75 draws as high as 18a under full load and you'd need a generator in the 3000w range to feed it.
The DLS-55 draws just over 13a under full load, and that's right at the max a Honda eu2000i puts out. In other words, a perfect match.
http://www.iotaengineering.com/dls55.htm
Iota DLS-55 with the IQ/4 brain module will run you 180 bucks at Northern Arizona Wind & Sun. (Note on that page, it shows 160 bucks until you choose the option below the price to add the brain module). You might find it a bit cheaper by looking around but NAWS has been around the longest and has just about the best rep.
DLS-75 with IQ/4 will run you around 290 bucks:
http://www.solar-electric.com/batte...12-volt-75-amp-regulated-battery-charger.html
Again, if you "did it right" and rigged all 4 batteries into a single bank, you'd need double the charger amps and double the generator. What I'm saying here is based on rigging a pair of those CR-260s into a 12v 260ah bank.
Now...solar.
Let's say you rigged for a 12v 260ah bank. Let's also say you draw the bank down 50% (the max if you want the battery to have a halfway decent lifespan). That means you've got to supply 130ah to get it recharged. Actually batteries aren't 100% efficient, so you'll need to supply 20% more amps than you took out in order to get it back to a full charge. So you gotta supply 166a to get it back to full.
So how much solar do you need? Well 166a x 14.5v (battery max) = 2407w. Now let's spread that over say 6 hours of good strong sun in a day (and that's actually a bit optimistic) - 2400w / 6 = 400w. So you're going to need at least a 400w solar array if you want to have a prayer of keeping up with your daily consumption (if you draw down 50% overnight).