You've got to either keep it hot, or cool it completely then reheat. If you let things partially cool and stay there too long you may be risking getting people sick. Reheating to whatever temp you like won't undo the damage caused by letting pork sit in the danger zone. You can kill the bacteria, but you can't remove their toxins with heat.
Short of pulling an allnighter, here's what I would do.
Plan your cook so that your butts are done about 8 hours before you want to serve them. Wrap in foil and toss them in your 120qt cooler covered with several towels and go to sleep. They will hold in a good 7 day cooler for 8-10 hours.
Get to where you are going in plenty of time and pull the butts right before you serve them.
You'll get "some" sleep and won't take the chance on letting the pork cool.. and won't have to reheat the next day, saving you time for other stuff.
If you are planning on doing this very often.. keep an eye out at used restaurant auctions for a big proofing box with a heater. They won't cook your meat, but they will hold at whatever temp you like for as long as you like.
4000 sq inch Wood Burner named Brutus - KCSB member/judge# 32129