I believe that the OP also wants to run their 15K A/C ... using the same generator that they choose for battery maintenance.
I vote for a couple of Honda 2000's, as with this combination you have generator backup redundancy. If ever one Honda can't be started, then at the least the OP has some 120V AC generator capability still available by using the other Honda. Only one Honda is needed for pretty good battery charging, so with only one Honda operating the OP can keep the batteries topped up - just not camp with the 15K A/C usable.