Tony, Portia--
This happened to me. They showed up at my door unannounced and demanded to know what was wrong with me. Why do I keep them away from the kids, etc....... (Ironically, they had seen the kids 3 times that week!) They're usual m.o. was to wait until things blew over, but that didn't work this time, things weren't blowing over.
I think it's wise to just act like nothing has happened and they may not do anything. However, if you are worried about it, perhaps it will help to arm yourself with a plan.
here is my experience, maybe it will help you:
When they showed up and demanded to know why I didn't let them see the kids, I told them (NDad & NStepmom) that I wasn't trying to prevent them from seeing the kids (true) that I had boundaries and I'm sure that they don't understand why (true). This is where I should have stopped, but I didn't.
They pushed to know why I needed any boundaries. I said that I have a lot of hurts from my childhood that I was working on healing and that our relationship is damaged because of these hurts. (true)
They demanded to know what hurts I was talking about and my Nstepmom pushed to know what they ever did wrong. I said that they don't respect my opinion about how my kids should be raised. They took great offense at this. they said that Of course they respect me, and they can't understand why I would think that they didn't respect me.
But just a few weeks earlier I had asked them to please talk to me first before making plans with my kids. ( they would take the kids aside and tell them to tell me that they were going to take them to the mall, etc) When I told them that I wanted them to ask me before inviting the kids places, they FREAKED OUT! How dare I suggest that they would need my permission to take the kids somewhere?? They hung up on me and wouldn't speack to me for a week.
Anyway, this interaction was the perfect example of them not respecting my requests, But when i gave them that example, they said that they only objected because it was such a ridiculous request. I said, calling my requests ridiculous is not respectful. My dad said that I needed to have a good reason for making such a request. I said, the only reason I need is that I am their mom. He didn't argue with that.
My Nstepmom then used her great "change the subject" skill to ask what they had done to me as a kid. I said that I wasn't going to talk about specific inicidents, that it would servce no purpose and that all they needed to know was that I was working on healing those hurts. I wish I could have stuck with this line, but unfortunately, they pushed and pushed. I wish I had used the broken record technique and just repeated myself, but I didn't.
I told them one of the minor stories of a time when I was very sad about missing my mother and my dad screamed at me and attacked me for being rude to my stepmom. At the time, he essentially said, How dare I be sad, that hurts my stepmom's feelings!
Anyway, This is a direct quote from my dad, "You are making that up, I NEVER did that and when that happened, it was clear to me that you were a very vindictive girl, you were deliberately trying to hurt (stepmom) and I didn't buy your manipulative tears and whining." It's almost funny if it wasn't so sad. BTW, I was eight years old when that happened, my dad thinks I was a vindictive eight year old.
At that moment, all my denials came crashing down. What I once saw through a glass darkly, I now saw face to face.
I didn't try to answer my parents questions after that. I just kept repeating that I do want them to see the kids, but it would have to be within my boundaries and I know they don't understand and I know that's hard on them, repeat, repeat, repeat. Eventually, they kind of calmed down and gave up.
So, that's my story. I apologize if I'm hijacking your post.
I suggest you get ready with some kind of statement that you can repeat to them ad naseum.
You do not need to tell them why. If they want to know why, it's because that's how you choose to do things. If they want to know why you choose to do things that way, it's because that's what you feel is best. Or "that's what works for us." You can acknowledge that it's hard on them, if you want, but don't say you're sorry.
good luck!