J.H.
I would not get him a bed based on if you fit in it too!!! If you put a twin bed against a wall and put up side rails; he should be fine. He will learn to stay in whatever size bed he is in. Too much freedom at that age may be too much. Ask his Pedi about his restlessness when he sleeps. I would break the habit of him sleeping with you. If you decide to have more kids; you need sleep and don't want to get kicked while doing so!! Comfort when he needs it for sure but put him in his bed! After a few nights of him risisting you and being a little tired; you both should be able to get some good sleep! Best of luck to you!