They could also take him on a day - trip to a beautiful place in the Hidden Leaf village. Maybe a peaceful meadow or a small waterfall. The beauty of nature would soothe him and being with his friends would make it even better.
One way is for his friends to cook his favorite meal, like a big bowl of ramen. Just the smell and taste of it would bring a smile to his face. And while eating, they could share funny stories to make him laugh.