You don’t have to announce your boundaries to them you just do them. If you don’t want to be around him when he’s been drinking then just don’t be. Get busy doing things you want to do. Go walk around a mall, go to the library – go some place that he won’t come and intrude on your wanting to be away from him. If the only place you go is to your daughters then you can expect he’ll show up like he did so find some new places to explore that you can get some peace and away from him for a bit.
There is always a flip side to boundaries – enforcing them for yourself because you can always bank on them stepping all over your boundaries. Once you set a boundary then you need to set a plan on what do you if and when they cross that boundary. You need to prepare yourself with a plan of action.