One thing to bear in mind - he will absolutely not want to have the kids much, if at all, if he isn't involved with them now.
Don't let that fear hold you back. He will want you to continue doing all the work, so no, he won't want to spend lots of time caring for them!
Oh, absolutely, he will TELL you he does. 'I'll go for full custody' 'You won't keep me from my kids' blah blah. All that shit comes out with every single last one of these abusive fucks and it has nothing to do with wanting to see the kids or be close to them. It's about a. scaring you into staying so he doesn't lose his setup and his servant, and b. control - they're HIS kids and you won't dictate.
When you split it's a different story. A friend managed this perfectly and I suggest you do the same. He spouted all that crap about you won't dictate blah blah mykids I'll have them loads, whenever I want.
Great, she said. I'm damned if you think I'm going to carry on doing all the childcare, the kids are your responsibility too and you will pull your weight. I will push for 50-50. You aren't going to get away with thinking that you can just pay me to look after them and not do the overnights etc. We'll both need free evenings and weekends to be able to move on, new relationships etc.
Oooooof you've never seen a faster 180 degree turn. What, she thought he was going to babysit on the weekends so she could go off and fuck her new squeeze? No way. He was going to be far too busy rebuilding his life to have them overnight, she shoudl act like a bloody mother and take care of them properly and no he wasn't going to give her free weekends...
Which is exactly what she wanted as he was neglectful, lazy and boerderline abusive to them too (smacks, shouting, poor diet, no bedtimes... the usual).
:)