I know its always an exercize in doing the RIGHT thing when it comes to these types of matters. In general, the LESS SUSPICIOUS you are of this type of stuff, and the MORE CONFIDENT in what the two of you are rebuilding, regardless of who calls in on the cell...who chaperones the kids at the pool..whats the history behind an unused box of condoms...the better off you are..
I would not let these things get to you where you feel you have to press him on it. Lets face it, the guy was seperated for a long time, and he was out and about socially, there are repercussions that result from that kind of a lifestyle. NOW, he supposively has recommitted, most of that is behind him, so maybe its best to ease off and TRUST that his ACTIONS will show you his level of committment to you when these things pop up by him DOING THE RIGHT THING.
Again, now that you are back together, you get to see first hand, just WHO it is you so desperately were trying to win back. I'd let him take the initiative with the female chaperone thing and WATCH how he handles it...if he leaves it up to you, thats a good thing, just tell him you don't think "we" need to bother her with that.. end of conversation..