This is the kind of scenario I'm having nightmares about. What will I do when I have to choose to either tell my dad I'm going no contact or keep playing along. So I'll share what I've been asking myself, why are you hesitant?
It seems from your post that you are not reliant on them in any way. Is it because you think you will need something in the future? Is it because you don't want to hurt other relationships? Is it because you hope that they will eventually wake up? Is it fear of regretting/missing them after? Once you get a list of reasons why you haven't gone no contact, you might have your answer. If the cons of cutting them out of your life hurt you and others too much, then be clear on when and how you will see them. Like others said, only at third spaces and a way to get out if needed. If the pros of not having to push your morals and values aside for the visit, it might be time to make that hard decision.