Our new Samsung TV has a an Optical OUT connection. We run an optical cable from it to our surround sound system. Anything that is connected to the TV will then play through the surround sound.
I suggest that you look for an Optical IN plug on your DVD player that will allow you to play the TV through the trailer speakers. These new optical and HDMI cables are a lot easier than the old yellow, white, red things we used to use.
2017 Wildcat Maxx 26BHS
2016 Rockwood MiniLite 2503S (2015-2016)
2012 Ford F-150 Eco-Boost