Just a thought. Instead of asking him to do something specific, why not allow him to find a solution? That will make it seem like his idea and he'll be more on board and empowered.
State the problem: "Kids feel disconnected from you/seem to miss you" Possible Causes: Don't see/talk to you enough/do enough with you... Solutions: Call more often, plan more outings, write emails....
Be careful with stating the problem. This could come off a bit like you being judgmental. Not saying you are, you're concerned for the kids. But missing him is a reality of his choices. You can't fix that for them, sadly.
IF HE KEEPS THIS UP, THEY ARE GOING TO MISS HIM. Maybe he should know how it feels to realize his kids are hurting.
(Hard, I know, Mama Bear!)
However, I have been using this technique with my H and although I usually think my fix is "better" , he has responded positively. Traditionally I have been the problem solver so it's good to hand it over. But this way, he is invested in the outcome. He feels heard and his opinion is valued. It's better all around.
I understand that the kids are hurting. But you're not going to be able to make him do what you think he should do to make that better. That's not who he is right now.
And expecting him to call everyday when it's not something that he feels is necessary---it's an expectation. So when he doesn't meet it, you probably will get frustrated with him.
Also, this sounds a bit (to me) that you, as the reasonable parent, are pointing out to him how he is messing up because of his choices.
He has to come to that conclusion on his own. So I would not hide the fact that the kids are sad and missing him. I wouldn't rub his nose in it either.
NATURAL CONSEQUENCES.
He doesn't keep in touch daily, his children are sad. Let THEM tell him this! Either with words or cards they make, or their actions.
I wouldn't email or text. Maybe the next time you see him, just casually mention that the kids really miss talking to him every day.... and let it hang....
A few days for him to mull it over won't hurt. See what he does.
Just be sure to keep the tone light and judgement free.
This is not a critical issue to resolve ASAP.
If he doesn't step up, I'd wait until he mentioned something about the kids seeming annoyed with him or distant.
Then reiterate: "They felt closer to you when they spoke to you every day."
Just give him the information and see if that changes his behavior.
Because if he doesn't WANT to call every day to talk to them because it would help them (being a MLC selfish booger), then you asking him to do it isn't going to change a thing. He'll either say he will, and then won't. Or he will do it and will resent it. Or he'll forget....
You asking him to do it is pressure.
(And for the record, he SHOULD call his kids every day! He SHOULD also respect and value his wife, stop acting like an a**crack, and grow the heck up!)
---(G)GGG
Me 54 Him 63 M 23 T 29 0 Kids Funny Farm of Rescues 12/12 OW-- 5/13 ILYBINILWY: A denied 9/13 Proof OW: ENDED 2/14 Got D papers on my BD I kicked him out for my sanity 9/14 He wants to "talk"?