Set up an interim dogbone of track after breaking down the Halloween layout and prior to pulling out the Christmas layout. My two and a half year old is just fascinated with the trains - here’s a couple short little videos:
http://www.myfirehawk.net/bsbpics/Tyler/MVI_0009.AVI
http://www.myfirehawk.net/bsbpics/Tyler/MVI_0011.AVI
You’ll need QuickTime or Windows Media Player with the proper codec in order to view them.
And here’s a short video of the train running on the whole layout: