I've been saving up boxes for a Space Day (for rocket building), but the kids informed me they preferred a Boxes Day over a Space Day. So, I set out different sizes and shaped boxes in the yard and brought out our cardboard set of building blocks.
These blocks were given to me by a daycare mom. The kids love them! Check them out: http://www.amazon.com/Melissa-Doug-Deluxe-Cardboard-Blocks/dp/B000A12YBW/ref=sr_1_1?ie=UTF8&qid=1407956291&sr=8-1&keywords=melissa+and+doug+blocks+cardboard
The kids spent the day (minus snacks, lunch, and nap times) building forts, hiding the blocks, playing hide n' seek, and pretending the boxes were cars, trains, houses, and so much more.
To go with our boxes theme for the day, the kids used glitter markers to color rectangle boxes.
Now you know the perfect Christmas gift: boxes. Lots and lots of boxes to carry their imaginations.