The Quick version of The Complete Children's Party Survival Guide
"The End of the Party"
If parents arrive early ask them if it is possible to wait until the end before collecting their child.
If possible keep waiting parents in another room or the garden.
If a child has to leave early ensure that this does not break up the party for the rest.
Use a helper to keep the children seated at the end, releasing them one at a time by using party bags.
Avoid releasing too many children too quickly.
If you need to talk to any of the parents, ask them to wait to one side until most of the children have left.
Avoid inviting all parents to stay for a drink at the end of the party.
For more detailed information on the above points see
Let's Eat (1)
Let's Eat (2)