We left the party around 4:30. Abigail fell asleep on the way home. This "nap" lasted 25 minutes or so.
She was not happy when she woke up. I gave her some milk and went ahead and fed Sarah. Well, Abigail ended up drinking her milk on the floor where she landed when we got home. The next thing I knew she was asleep on the floor.
Longer story shortened: Sarah is fed and sleeping and I am sitting next to Abigail's bed waiting for it to be safe to leave-when she is sound asleep.
I think keeping her awake until her regular bedtime would have been the lesser of two evils. She would have been cranky in both instances, but a whole lot less if we had kept her up.
Lesson learned and noted for next time.