Hi Catlover,
I had the same thing happen to me. My ex would wander into and through my home and I didn't like it. I felt uncomfortable and awkward in my own home. I wanted to deal with the situation without a confrontation if I could so I chose to use body language as my first port of call. It took some planning but I made sure the girls were ready to leave well before he was due to arrive and then I basically waited for him. When I saw his car arrive (or the door bell ring), I called the girls to the door with their stuff before I opened the door. Then I opened the door and let the girls out while I stood across the doorway - kind of like a sentry blocking entry. It was a simple body language move that meant it was automatic for the girls to go out to meet him and leave with no excuse for him to come through the door.
I did the same when they were due to come home. I opened the door and then stood blocking it with my body and said "Hi girls, come in...thanks for bringing them back...Bye" No room emotionally or physically for him to come in.
I did this consistently and he got the message. He doesn't even try to come in anymore. It seemed a bit tough not to let him in at all but I needed to do it to set the boundary and for him to get the message that this was not his home to wander in and out of. Now that he has got that message, there are times when he has had to wait longer and I have actually said - "You can wait in the lounge if you like" and that is where he has stayed. But I had to establish the 'no entry' boundary first. Now e doesn't enter without permission.
If he hadn't got the message that way I was prepared to actually say to him "**** I am not comfortable with you wandering into my house so when you collect the girls I'd like you to wait at the door and I will bring them to you" and then be prepared to repeat the same statement (broken record it's called) over and over if he tried arguing with it. It stops you from getting into a mode of defending yourself or getting talked around. Just stick to your prepared statement.
That's how I did it and it was effective for me. I hope this helps a little. Sometimes they just need to have their thinking adjusted to realise that they no longer have rights to you or your home.
I know this is a tough time. Remember God is with you