This will be oversimplified in a post, but when you get into purchasing solar panels you need to understand the basic differences between polycrystalline vs monocrystalline solar panels as well as the other options out there.  

You don't mention if you want to permanently mount the panel to the trailer or keep it portable.  This can make a difference as to which type of panel you buy. You also need to make sure that 100w Poly panel will deliver enough energy to meet your projected usage, keeping in mind that this will only yield a guideline and not real life. I remember a fella a few years back, that was very technical and spent countless hours calculating exactly what he'd need to put solar on his trailer. He spent almost a year calculating and building the perfect solar system for his Scamp. He forgot one step, he never field tested it. When he went on his first week-long vacation with his new system off the grid it was quite a bit deficient in what his actual needs were even after all his calculations and the trip was quite a disappointment.

I use a scalable, portable briefcase solar system that I can add or subtract panels as needed.  They can also be adjusted to be at the perfect position throughout the day vs permanent roof mounts.  Lot's of ways to approach the solar and just depends on how you want to do it.  First step before buying solar though is to replace incandescent lights with LED to get your power consumption down to the minimum.

There are quite a few members with solar installations, so we should get some more feedback in the days ahead.