I also have the Morningstar Tristar PWM 45 because I had future expansion in mind. I'm running 2 x 140 watt panels with 2 x 6V GC batteries. I have found that I don't really have a need for expansion at this time. But the Morningstar controller is really nice and fully programmable if you choose to really customize things. Also diversion load capable. I originally thought I would also be eventually buying the $100+ remote display panel, but I got by fine with just a volt meter that plugs into the TT 12V socket. I now have a permanently installed 12V meter and that's good enough. Of course I do hook my laptop up to the controller fairly often and use the MSVIEW software to see charging amps and other details that can't be determined by a voltage reading and controller status LEDs. It really is far more controller than you'll need for a single 100 watt panel, but it is definitely a nice controller.
Solar plus a smart controller is a great way to maintain batteries while unattended. A 100 watt panel should do a great job and keeping your batteries fully topped off and ready to rock when you show up. A second panel might even fully charge them on a daily basis while the camper is in use.
