One thing you should seriously think about is the difference between 2 wheel and 4 wheel drive.
One of my friends uses a 2 wheel drive van for towing and camping. She is notorious for getting her rig stuck in muddy fields. Sometimes she can get going again if she unloads the horses to lighten the load. Of course, this means she needs someone to walk behind her leading the horses until she can get onto a paved surface. Other times she gets so badly stuck that someone has to pull her out. Of course, this usually means they need to unhook from their own trailer, perform the rescue, and then hook back up. Good thing she has good friends!
Mindful of my friend’s mishaps, I looked at 4 wheel drive vans for camping a few years ago. I found the options pretty limited. The big issue is that the 4 wheel drive option tends to drop the weight capacity by several thousand pounds. Looking at the situation with brutal honesty, I wasn’t going to be able to stay under the safe maximum weight limit with two humans, two horses, a steel trailer, and all our gear.