If I was you, I would 装修好个厅 => change the sitting room to a large bed room for your kid.
i.e. there are no sitting room in your flat. Then, everyone should stay in their room all the time !!!!
And you can place a TV, PC, sofa in your kid's room as it is large enough. Most of your time will stay with your baby, that room will be your sitting room (but not for your 62's) and bed room for kid at the same time!!!!
i.e. Force your 62 stay in his room all the time!
Is that work?