Enlist the help of older kids to help keep the younger ones busy. Small toys purchased at the dollar store make great prizes. A great activity that kids of any age enjoy is painting. Most craft stores sell small, inexpensive plaster knick-knacks for every season. Don't forget to recruit help in the kitchen also.
Guests are usually more than willing to help serve refreshments or stir gravy.
Many foods can be prepared and frozen ahead of time. Many can also be prepared and refrigerated the day before. Go over your menu and see what can be stirred or simmered the day or night before. Vegetables, meats and fruits can also be cut up and refrigerated. If someone asks what they can bring, don't be a martyr.