I would consider buying 2 100watt panels, (or 2 80 watt) mounting one of them on your trailers roof, and keeping the 2nd as a portable option that you can easily hook up and place where/when needed. I have 300watts on my roof, i sometimes am in a shady area so i have another 60watt portable panel that i can bust out and setup if i desire. I like having both on roof and portable. If i could only choose one or the other it would be on the roof. If you are set on portable only i would use 2 smaller sized panels rather then one huge one as it will be easier to move in and out of your trailer and store.
Solar is great, you will like.