Cool - made two today! (Then a party to decorate them.)
Let the houses "set" on a flat surface after they've been in the oven. (Trouble in previous years from warped pieces.)
If it breaks don't panic, you can ice it back together.
Make sure the icing is quite thick (egg white in mix helps with this.)
Use what ever tins you have in the cupboard to support it while you build it - first walls and then to stop the roof pieces sliding off.
Get some cardboard and cover it with tin foil for a base. Make the base bigger than you think you need. (The children here like to make gardens too to go with the houses.)
Probably a bit late for you, but we save the trick or treating sweets for an eclectic mix of stuff to use to decorate them.