What to do on the nights I can't get to the gym

My living room is like a long hallway with barely enough room to walk comfortably between the couch and the TV, and the only computer I have besides a small phone is a desktop beside our bed in a very small bedroom. So no room for work out videos. Usually when I workout, I either walk during the day time (but since its summer its now too hot to take my little guy) or I go to the gym. This has worked great and I really enjoy it the problem is I usually only get to go to the gym when my little guy falls asleep and with it being summer and lighter later he hasn't been falling asleep until almost 9pm and the gym closes at 9:30pm so no time for a workout. I hate rushing our bedtime routine so I can get to the gym and I hate not getting a workout on the nights he's up late. I would love to have a workout I can just do anywhere off the top of my head but have no clue at all how to put one together. I had knee surgery in December so my knee only bends at a 95 degree angle so things like lunges or anything to do with stairs is very hard on my knee. Any help trying to develops a routine I can do at home would be amazing. thank you so much