For a sweet Christmas party activity, try this:
Purchase one Anna's Gingerbread House per child.
The price is right ($8 each) and the gingerbread is delicious.
Truck it on over to Ye Olde Fashioned Lolly shop and unleash the children.
Mix up a HUGE patch of Royal Icing (powdered sugar + egg white + lemon juice).
Fire up your piping bags.
Ours lasted, in their fully assembled and decorated state, less than an hour.
If you prefer to buy your own, Ikea has (of course) provided an easy template and fool-proof assembly instructions here.
Love those Swedes.
(Hot Tip: do NOT follow the Anna's assembly instructions, which involved melting 200g of icing sugar over a medium flame. This results in a sticky, molten mess and will leave you with blistered fingertips. I can barely type....)