Escalate the office arms race the safe foam-ammo way.
Baby, it's cold outside! Which is an excellent reason to stay inside and play with some toys, or maybe learn about science, or perhaps help Mom and Dad take care of a younger sibling. Possibly you could also move all the furniture and have a big pillow fight, or color or... okay, maybe you COULD do some outdoor things at some point. Just, you know, wear a jacket or some mittens. It'll all work out fine.
Because that's the magic of January. Grey, cold, and kinda boring. One must make one's own fun, right? SO GET ON IT, PEOPLE.