Bring a bale of dry wheat straw along on the trip. This can be shaken loose and spread on the floor of the dressing room as soft bedding, over which you can throw blankets and sleeping bags. When you've finished using it as bedding, you can use it on the journey home in the horse stalls, instead of the usual shavings.
Particularly if you expect strong winds, rain or a sharp drop in temperature, you can weatherproof the trailer. Use tarpaulins and blankets to hang over the walls of the trailer to keep cold and water out and heat in. Tie, clamp or nail your tarps or blankets in place at the point where the walls and roof meet. Check your trailer before you set out on your trip and decide what the best method for hanging the blankets will be.
If camping with a group, it's a fun idea to recreate a Wild West wagon trail. Circle your wagons by parking your trailers in a circle and making a campfire in the middle. When the events of the day are over, everyone can sit round the fire telling stories and jokes and singing. Remember to keep your fire small and not to leave it unattended at any time. It should be extinguished before you enter your trailer to sleep.
An extra tarpaulin and two poles can be used to create outdoor living space by attaching two corners of the tarpaulin to the trailer and a pole at each of the other corners. A bucket with a toilet seat purchased from a camping supplies store can be turned into a potty. A large lidded bucket can be used to store water for washing. A doormat helps keep dirt outside. Do not forget at least two portable, battery-operated lamps for lighting.
If you are overnighting with kids, you can have a competition for the best decorated dressing room. Make sure the kids know about this before they leave home so that they have a chance to bring decorations from home with them, such as balloons, streamers and posters for the walls.