We had a 2003 Caravan. Tranny was acting up so I put it on my car trailer to get it to the shop. The van sat so low that it high centered on the ramps/trailer when I got it half way on. Little throttle got it up on there the rest of the way. Ended up catching the muffler on a lip and pulled it off the pipe. So if you go the trailer route make sure you have proper clearance to get it on there.
I love flat towing but I would not bother towing that 4 down, trade it in for something else that can be towed 4 down would be the way to go.
I hate tow dolly's but if you want to keep this van I think it is the most practical way to go.