How do you say goodbye?

[mom-in-alberta]

I don't think I would have a "party" exactly. But maybe a special treat on the kids last day, or a little baggie of toys/treats etc, with a note saying "thanks for being here". It may not have been the perfect arrangement, hence the termination, but then you can end things on a positive note.
And I think a quick conversation, face-to-face, accompanied by a written notice is the way to go.
Good luck!!