At wikipedia you can view transiting tesseracts as well as 4D spheres rotating. I think that it is possible to do a computer animation of a 4D tree growing.
Then you put it out on the lawn to emphasize and promote multidimensional holiday thinking. Really, millions of people viewing a representation
of growth at hyperspace might inspire passing mathematicians.
Better yet would be something like a string of holiday lights at a geometry that lights up to provide the 4D view rather than a snow bedecked flatscreen TV.