After waving off your in-laws, you can get back to sorting out the spare room. Strip the bedding in the guest room and wash, while fully sanitising all surfaces in the meantime. You could even give the mattress a freshen up by sprinkling with bicarbonate of soda before vacuuming.
Now might also be a nice time to refresh the space, breathing new life into the room for the year ahead. Pack away any extra clutter and open the windows to air it out, then add a few statement pieces back in with some bright cushions, wall art and accessories plus a potted plant.