S.W.
I guess I'd think of some place or some event that you think he'd like and then next time you two are hanging-out, ask him! I'd probably keep it kinda casual. Then if he says yes, you can move things slowly in that direction. But, you know him best, so maybe he'd appreciate the direct approach better!
I have a girl friend (with 3 kids) that had a guy friend at work and they talked over coffee all the time. Then she got divorced, and one day she just "laid it on the table" (her words) that she was interested in him. They are happily married now!
And we single moms do date all the time...it's not a sin... ;-)