Div, not a control freak, you just know when something doesn't make sense.
Heres MHO - guys will hang on to you (when you leave THEM) , until they find someone else to fill the spot, they can do it real quick and even if you don't give a rats it can still jar you a little. He may even want the boys to dob him in to test your reaction. This stuff is far from over, the breakup hasn't really been tested yet. Just wait till he breaks up with a chick and then rings you whining and drunk about how he is so hard done by (oops sorry - that's my life!).

Aaanyway - why don't you try writing a letter and give it to him to read next time you pick up the boys. Something along the lines of - look we haven't addressed this yet and it feels wierd to be doing so but I would like to sort out this situation out before it happens. If and when I become interested in someone else *rah, rah* I want you to know that I will not be introducing them to the children until I have established blah, blah, blah and I hope you could do the same. Explain it is not about you and your feeling (or lack of them) towards him, and even if/when you are ready to hit the scene again the children may not be ready for it and this is that main concern.
Him seing someone else is totally up to him, but it is far too early for the kids. This whole "daddys new friend" crap always ****es me off as most children are not fooled at all.
I think if you do it now, it can avoid any more bollocks from him, because if you do object later he will read it as 1) you still really love him or 2) remind you that YOU left him and if you hadn't this problem wouldn;t be happening now.whine.

good Luck Div,