Organize a Moving Sale
Once you've figured out what you want to pack and what you want to purge, get the kids to help you organize a moving sale. They can help you sort through everything, organize it, inventory it, and price and tag it. Let them know that the proceeds from the sale will be used for something for the family. In fact, you can have a family meeting and vote to decide on what that might be. Maybe it's a giant flat screen TV for the new house, or maybe it's a chocolate lab puppy. Whatever it is, the more invested the kids are in the goal, the more helpful they'll be with organizing the sale.