DD turns 4 this year, and it'll be the first year we've done a birthday party for her that's not just cake at her grandparents' house, as she wants to invite her preschool class. We're hiring a hall and going to keep it pretty simple - just a picnic tea, dancing, pass the parcel etc. Is there anything you wish you'd known to make birthday parties go well? What makes a good party for parents as well as children?