Well, I can see both sides on this issue. I tend to gravitate towards the "need to know only" basis. I totally understand the need to educate people and break stereotypes and de-bunk myths, but at the same time, I am extremely paranoid about information falling into the wrong hands (unlikely, but still a concern for me). I like Fred Thompson's line during a Republican candidate's debate last year when he was asked if he has any guns - he said something along the lines of "I own a couple of guns...what they are and where they are is none of anyone's business."
That being said, I am caught in a bit of a bind. My wife is not crazy about guns but tolerates them (been working on her for a few years now - the fact that she willingly signed off on my PAL application a couple of years ago is a step in the right direction). She also runs a home-based academics/schooling business which has a lot of children come through - as a result of the licensing aspect of our business, we are legally obligated to divulge the fact that I have firearms in the house - she is not crazy about this and neither am I. Now, that being said, during initial screenings, potential candidates don't actually meet us at the house until they tell the screener that they are OK with the fact that one of the homeowners is a gunowner as well. I don't exactly live in the most gun-friendly area either, so it's been an uphill battle.
That being said, divulging one's interest in firearms has helped me to turn several people around to better understanding the thought process of a gun owner. My brother, who found out 3 years ago that I have picked up target shooting and general firearms as an interest, first reacted with disdain and the typical shock and awe that those who have been conditioned in an anti-gun environment tend to emanate. However, over time, he has asked more questions, some very pointed and perhaps argument-driven, but I have calmly answered them with supporting information and real-life examples. At the very least, he knows that I am an educated gun owner, and not one of the many left-wing-created stereotypes. I have even given him a tour of my gun cabinet. Him and my wife are the only ones who have seen what's inside the cabinet.
At work, it's a pretty white-collar office environment, and very, very few people are interested in guns, much less have a licence. Plus, with all the ridiculous laws that govern workplace co-worker interaction, I really don't say too much about anything to anyone, though I'm pleased to know that one of our executives is a duck hunter.
Some of it is also cultural as well. I imagine it would be far easier in a rural setting to discuss gun ownership. In my case, I live near the big city, and not only that, I am a "visible minority", so that in and of itself garners me some odd looks as a proud gun owner. I've had more than my fair share of, "what are you doing with guns - I thought only White guys own them." It's no different at my church, where I was an elder and my wife the children's program director - lots of people see guns and faith to be mutually exclusive. Well, at the very least, I am helping to chisel away at media-created stereotypes of gun owners.
Still, while it's great to discuss all things firearms, in the big city (especially), one has to be vigilant, since you never know who can be the unintended recipient of that kind of information. So I tend to temper my exuberance with a pinch of caution, and feel people out and vet them fully before even breaching the topic of firearms. But that's just my own humble two cents...
Now, to the original poster's situation, I have a daughter as well so I totally can relate (well, sort of, she's still a toddler right now) - as someone else has helpfully suggested, if the character is shady, my concern would be his intentions with my daughter rather than his intention with the guns. Unless I know him very well, I wouldn't divulge much information about the guns that I do have and what they are used for.