Can you not time the drive to co-incide with when you would put him down for 1 nap, or half an hour before you would normally put him down? We've travelled a few times during the nightmare period and just try and get as much sleep happening in the car as poss.
Potty training, well, just don't stress about it. It's not like he'll never get out of nappies if you have a couple of days backsliding

Keep your routine as much as poss but don't expect too much. You might find he does loads better when you get back home for having a bit of a change anyway.
By the sounds of things, you need the break! It won't be a disaster, and it will be good for him to do some new things as well as you. Once you're back in familiar surroundings you'll re-establish your routine no problem - it's only 2 days, not 2 weeks.
xx