You need to document that she’s alienating the kids from you by telling them that you were abusive to her. That needs to be addressed in court.

Yes you are supposed to foster a relationship by getting your kid ready for visitation time (if the kid is interested) to be picked up for scheduled visitation and you don’t supposed to speak poorly of her.

All this other stuff isn’t falling into required fostering.

Tell your ex to petition courts for visitation (in amicable divorces parties could decide on their own visitation schedules but in general it’s better to go through courts). And then when visitation is established, you have to let kids go with her if they want to.

All these other things like her coming unannounced or drop off things unannounced need to stop and isn’t something you are required to allow. Do not open the door. Your kids aren’t supposed to let her in either. She doesn’t live there. It’s wrong. Let her get court ordered visitations. And even then she’d not be coming inside your house to pick up the kids

You keep saying you can’t block visits. You can’t block “established” visits. No court will require you to allow exes to drop unannounced in your home. You can’t foster visits that interfere with your life. No judge would ever put anything in custody order (temporary or permanent) that allows visits happen haphazardly whenever other person wants and that visits must happen in your house. That is simply never ever happening.