Adjusting whipped cream to hold its shape longer?
Your best bet is probably gelatin stabilized whipped cream.  This recipe from Wilton gives you an example of how to proceed.  You can google many other results.



Depending on your tastes, to compliment gingerbread, you may also consider some alternate frostings which will hold up better at room temperature and taste great:


White chocolate ganache (sample recipe from the Food.com)
Cream cheese icing  (sample recipe from Martha Steward)


And I have to mention, in a completely different direction, a lemon glaze could be spectacular on gingerbread, although very different (sample recipe from Martha Stewart).