I'm not sure what you want to say to your sister except that you know that the two of you are at odds but you want to be able to see the kids from time to time. Maybe see if you can arrange a visit once a month?

For them, just that you're thinking about them and miss them but you have to sort some things out and they can call you any time? Which is true and doesn't malign your sister.

It's a tough one to be sure.