Rhap, Maybe something to the affect of, 'Daddy and Mommy aren't going to be together anymore. Daddy still loves you, but Daddy needs or wanted to be with (her name - Has the child met her?) right now.'....

Or something along those lines. I would hate to think that these children will somehow feel unloved by their father. Also, point out to them, that Daddy's and Mommy's don't always stay together but Daddy's and Mommy's will always love their kids'.

I don't know if the guy misses them or not. If not, I wouldn't have the heart to tell a young child that. Maybe I would say something like, right now Daddy is confused. I sure he misses you whole bunches but, for now, Daddy needs to find himself. .

??? I may be way off, just throwing something out there.