OP, you mention specifically about wording of the conversation.
I am sure I’ve posted before, but I would start with a chat with your partner about both of your expectations from the relationships going forward, limits/boundaries, and how you’re feeling, so you’re both communicating the same thing.
You can start and end the conversation with the theme of ‘anything we say isn’t with the intention of causing upset, but with the intention of us finding a way to move forward’ (or similar, whatever your aims really are) and also being positive about the fact that whoever is involved in the conversation is happy to sit and talk about needs discussing.
My recommendation would be to do a bit of research about ‘I’ statements, they’re really good at explaining how you feel without apportioning ‘blame’ to another person.
If this is (which I understand from your posts) a repeated request, I’d also recommend some reading about assertiveness and dealing with a ‘broken record’ - there are some excellent CBT resources out there which are useful.
You do not have to pass your child to anyone who makes you feel uncomfortable for any reason.
Whilst there is joy to be had in a healthy relationship with grandparents, there is also a good lesson to teach your children in not doing anything with someone that makes you feel uncomfortable.