So I don't have kids and I've never really dated after I was diagnosed with bipolar disorder (I am in a relationship, but we met on line and he knew all about it before we met in person).

So I may not have good advice but here it is: If he asks about your kids can you just say they are great and talk in general terms about them (this one is in such grade and likes x,y,z). And if he asks why they don't live with you would you feel comfortable saying : It's a complicated, sensitive topic that's hard for me to discuss at this time. I hope you understand."

And if he does really care for you he should respect that boundary.