Also relevant in this discussion is weight ratings and tongue weight.
Useful page with some acronyms and definitions:
http://www.hitchingup.com/GVW-VGWR-TW-GTW.htm
I suspect that one of the issues with a mini-van is that you're going to want to put people and stuff inside the mini-van. Not that you won't want to do this with a truck or SUV but they tend to have higher GCWR... though that depends on a lot of stuff.
Also, most mini-vans don't come with factory installed hitches to my knowledge so make sure the hitch that is installed is capable of supporting the weight and it was installed correctly.
Also, this was recently on reddit and seems relevant. Basically, don't overload the back of the trailer.. you want to balance the load but you should favor the tongue:
Bottom line is this, do your homework and talk to a trailer dealer in your area and make sure that the people (parents/mentors/whomever) that is responsible for towing the vehicle understand all of the necessary legal requirements and steps for connecting and towing the trailer safely.
Don't let any of this scare you. This stuff really isn't complicated once you figure it out. Towing can be kinda fun (that's the North Cackalackian in me coming out).
Also, make sure you're in compliance as far as insurance goes. Some auto insurance can be funny about towing trailers... Make sure the tow vehicle is covered and the trailer is covered as well and the stuff in the trailer.