I don't see any issue with using your minivan (without the tent) as there are always several people sleeping in their automobiles when we happen to overnight at Wally World.
Many have stated that there are rules or some kind of etiquette that must be adhered to but that is simply not the case. It is wise to setup as little as possible so that it is easier to get up and go in the morning. No awnings, barbecues, or chairs make for a quick departure.
As for deploying slides, unhitching, running generator, or dropping stabilizers there are no hard rules. I've seen all the above done on many occasions and it didn't bother us a bit, probably best to find a corner or edge of parking lot if you want to utilize these functions.