one might want to bring:
a good gift
a good joke
a warm hug
and a LOT of patience.
Especially when one of the people in attendance has pneumonia.
or when the children become unsupervised often.
or when one of the unsupervised children is a villain.
or when two family members pull you aside separately to complain about one another.
or when there is a neighborhood wide garage sale.
all hypothetical, of course...
hypothetically, I may have scored some free toothpaste- making the day a total success.