As the father of 4 daughters, give ya some advice.
1. My little girls (whether they be 2 or 42) are always my little girls. I raised them to show proper respect (I am old school on that), and I demand anyone thinking about dating them first and foremost show them proper respect. That is non-negotiable.
2. Where and when I was brought up, you showed your elders respect. Elders whose children you wish to date, doubly so. It ain't worth getting your ego in a tuzzle. It is what it is and it is simply showing proper respect.
3. If you have a similar interest as me (Fishing, shooting, hiking), etc that is cool. I might even be glad to share my insights with you and chill, provided rules 1 and 2 are met first.
4. As long as 1 and 2 are met, I have no problem being "guys" around each other, heck we could even be "friends" a bit all limited under items 1 and 2.
I know sounds snooty and old school, but it is what it is. When I first started dating my wife (in high school), I pulled in the driveway, parked the car went in and met her father and mother face to face and let them both look me in the eye and size me up. I found out a decade later, I won them over that night. I don't ask for kissing my backside or nothing like that, in fact, I would find that creepy.
So to your original question, be honest, show him respect, treat his little girl right, and let everything else fall where it may. If he gives you grief on your guns, maybe offer to go out shooting with him. Let him try it out, you can try his out (if he is game) you might both learn something. Course, I would definitely make sure I have 1 and 2 covered solidly before I went anywhere alone with him with a loaded firearm.