I (44m) am struggling to appropriately deal with my parents' (73F, 75M) behavior around my children (12F, 10M) and neice (11F)

How should address this with my parents?

My grandmother passed away last October at age 98. She lived a long and fruitful life, huge family, traveled the world, was widowed just a few years ago. Absolutely nothing tragic about her passing.

My mother has a strained relationship with many of her siblings, and in these final years they have all had many squabbles over my grandmother's care and estate planning. Some of them have not been on speaking terms for years as a result. Shortly after my grandmother passed, all of the siblings got together to finalize the arrangements; according to my mother it did not go well.

Initially my mother told me that it was completely up to me if I came to the funeral as she was feeling quite negative about how everything was being planned. It's a 5 hour drive from where I live and in the middle of nowhere, but I said that I certainly planned on attending, my grandmother was big part of my childhood and I wanted to be there. My mother said that was nice, but I definitely didn't need to bring my family all that way (I have 2 young kids).

We spoke a few days later, and she truly wanted me there for support despite initially saying she didn’t care.  I reinforced that I definitely planned on coming, and would likely bring my family with, even though it would be a little logistically challenging since it's such a long drive and in the middle of nowhere. She said that either way is perfectly fine with her.

A few days passed and we spoke again.  I confirmed that my family was definitely coming, and I would let her know what the logistics were. My mother offered up that staying at her place  for the night. I said I'd consider it, though her house kind of out of the way for us and would add driving time.

My wife and I explored options and landed on a BnB in a town halfway between our house and the site of the funeral. Logistically it made the most sense since my kids has stuff planned on both the Friday before and Sunday after the funeral...and the drives each way would be quite long otherwise. So I texted my mom and told her what our plan was and that we would see her at the visitation, stay for the funeral and any luncheon type stuff afterwards, and spend some time with my parents after everything is over before heading back to the BnB.

I got a call from my father a few minutes later, irate that we were "changing our plans" and not staying with them. I respectfully pushed back and said that I had never agreed to staying with them, and that the fact that I'm bringing my whole family there should be enough especially considering my kids barely knew my grandmother and this wasn't something they really wanted to do. Later I got more texts from my mother, telling me that I was being very hurtful.

We went to the funeral, and we were one of the few families who showed up from far away with our entire family in tow. My parents, especially my dad, were extremely icy to me and my wife. I did everything in my power to be warm, empathetic, present. We brought flowers and planted a tree in my grandmother's honor.

After the funeral, there were several weeks of radio silence with my parents until they called me a few weeks before Christmas. It was a challenging conversation, but I felt like we landed on something we could both be OK with...they recognized that I am going to always prioritize my own family first and that sometimes results in not doing everything they want. I recognized that they were hurting. A few things they said annoyed me, but I got past it. I agreed to have my family come down and spend a few nights with them between Christmas and New Years so we could celebrate the holidays together, and my niece (let's call her Hope) was also going to arrive a couple days before we do and spend the whole week with my parents.

The handful of days we spent there were fine. They were perhaps a bit distant, but overall pleasant and they enjoyed spending time with our kids. We all exchanged gifts, had meals, played games, etc. All hugs and pleasantries as we hit the road to head back home a few days later.

On our way home, my daughter said "Hope told me that before we showed up, your parents said they will never forgive you for not coming to their house after great-grandma's funeral. I had to explain to her all the reasons we made the choice that we did." This struck me as so unacceptable for so many reasons:

A. On what planet is what I did an unforgivable offense?

B. Why are they saying this shit to my 11 year old neice?

C. How can they say this just before spending a few fairly pleasant days with us?

To add an important bit of context as well, this past Summer we spent a 1 week vacation with my parents to celebrate their anniversary...my niece was there for that as well and she shared a bedroom with my parents. On that trip, Hope told my daughter "Grandma thinks your mom is controlling". So they were talking shit about my wife to/around my neice then as well. When we found out about this we were annoyed but decided not to approach it.

I'm struggling to figure out how to address this with my parents in a way that isn't going to just torpedo everything. Knowing my parents, they will deny ever saying anything. I also don't want to throw my neice under the bus. My parents notoriously are bad at conflict resolution and often take things extremely personally and play the victim. If I come at them at all directly or confrontational about this, they will get extremely defensive.

TL:DNR - My parents talk shit about my family to my niece, and I'm struggling to find the best way to address this with them.

In this situation, would you suggest I approach this directly with my parents? Any tips on approaches? Am I off base here?