Keeping dog happy/entertained during crate rest.

Can anyone offer any suggestions to keep him happy? We are almost 3 weeks after surgery and the last couple of days he seems quite sad. He doesn’t like chew toys but occasionally likes a bone to chew on. I’ve been giving him a lick mat every day which lasts about 20 minutes. Generally he just loves to spend his day cuddled up or playing with his sister. Last thing I want is him depressed 😭