On the one hand, when we were in our early 20s, this was a little skivvy.I could never understand what a recent college grad would have in common with someone I considered to be a parental figure.You might be dating their dad but you're a stranger to them, after all.So don't scare them away with OTT gestures or make it seem like you're trying to replace their mother.
And if you don't see a future with him, break it off before you meet his kids, as you don't want them inadvertently involved in your 'mess' too.
Take baby steps and let them slowly open up to you as they get comfortable with having you in their lives.
Being too full-on with the kids might also make your man regret his decision so play it cool.
They share a history and they created life together and looking at his kids will always remind you of her existence.
In fact, you might also see her often, as they co-parent their kids and you come across her during drop offs or pick-ups. Be happy for him that he has a good, stress-free relationship with her or give him the support he needs if she's the difficult type.
If he asks for advice related to a situation with his kids, be as neutral as possible and make it clear to him that they're his kids and that, at the end of the day, he should be the one making these decisions.