I've talked the property owner into leaving them where they are now.
There's a screen of bushes between the hive and the grassed area. The earliest the bees could be moved would be Friday night, which means that the straglers would be hanging around on Sat night all lonely and lost with no home to go to and probably itching for a fight.
I pointed out to her that if she had called last week, it could have been sorted out in time.
It was a nice sized colony, so I've suggested if she still wants to move them on sometime after the party, I'ld willingly give it a go then. It could be interesting.
Worst thing about possums is what they do to your fruit trees. (they can clean out a tree in a few nights) Luckily they don't hang out in my area as the locals care for their fruit trees too much.