Host a barbecue at someones home. Or go outside, to the park. Remember the sauce. And the beers. Combine it with quizzes and contests, or just enjoy the good company.
Go out on the town. Eat at a nice place. Enjoy some wine or just cool water, and feel good.
Sit down. Find the low gear. Be creative together. Cut pieces of paper, paint, draw, create clay figures. Either as part of an exercise, or just for office decorations. Maybe for special holidays. Invite family, even.
Go to the theater, or go see a musical. Unwind.
Acquire some fun toys, and play with them once in a while, to unwind and laugh together. An electric car, a toy robot, a quadroscope, whatever.
Never miss. Always nice.