I made one weekend (with some success) the solar system model. It's not to scale at all, which is a bit annoying, but it's sort of nice.
|Mobile solar system by Canon.|
If you don't that, how about a model of a Subaru telescope, the structure of the Sun, a sundial, or a moving model illustrating the difference between the Copernican and Ptolemic models of the solar system?
|Copernican and Ptolemic Solar System models|
Perfect Christmas holiday activity for older children I would say. My two are still a bit young though. :)
Just a comment that the title of this post was a reference to my post "Astronomy for Young Children - Colour the Solar System", which is actually my most read article on this blog!