It can't take more than 4 hours total (preferably not all active) on the evening before. Some advance prep could be done a day or two before that evening-before-the-party, if necessary.
I'll have about 30 minutes on the evening of the party to assemble, add finishing touches, etc.
Transporting is no issue - just walking up the street.
I wish to bring something unexpected, so no Buche de Noel.
No Paris-Brest, as I'm serving that a few days later, on Christmas Day.
No out of season fruit, though I might consider frozen raspberries for a filling.
No steamed pudding. That's already accounted for.
Your thoughts? Thank you, everyone. ;o)