from what i've gathered you're better off if you have a kid.
don't know about charity events, though.
I've shared my experience before. Went to the Caravan event a few years back when they stopped through Fayetteville (Ft. Bragg actually). It was the year after the Superbowl and Smitty had been my favorite player since he first got here. All the other players there were pretty much scrubs - it was Rod Smart, Colin Branch, and I think Jordan Carstens. So, obviously, I was mainly interested in meeting Smitty.
When I got there, they were giving out the team photo from that year to have signed by the players. I was never big on autographs, and if I did get them it was for my own memories, so if I didn't get them, no big deal, I can remember something without that... I got there, was handed a picture, and stood in line... Got all the way up there, was next in line to walk across the table with all the players and someone from PR I guess came and got Smitty right before I walked up. So, I walked through, got all the other players autographs, which I really didn't care about...
Smitty was doing some stuff with kids like playing catch, taking pics, laughing, talking, stuff like that. He walked off into a RV and then came back out, I figured that I had been there long enough, I may as well at least get my favorite player's autograph and get a chance to talk with him before I left. A security guy walks him back to the table, and for some reason still unknown to me other than just being young and stupid (I was around 20 then), I walk up to Smitty and ask, "Hey Steve, I was waiting in line earlier before you had to leave and didn't get your autograph. Do I have to go back and wait in line now?"
No response. Just a look like he was burning me alive with his eyes. If he could murder me with a facial expression, he was trying to do it. I felt like I saw what Anthony Bright did in the film room before he got his face crushed, lol. Steve never said anything, just looked and kept walking. Really awkward... Finally, the security guy looks at Smitty, back at me, back at Smitty, sees what's going on and interjects, "Uhhh... Yeah... Uhhh... Yeah man, just get back in line! You gotta get back in line!"
I walk back to the back of the line regretting that I ever thought I could walk up to Smitty and speak to him. I never ever want to come off as a fan when meeting an athlete/celebrity face to face, and I broke my own rule and I felt like an idiot for it. I watched as other fans went through the line and Smitty was a completely different guy with kids. He was like a kid and interacted with them naturally. With adults, it was hit or miss. Some he was completely cool with, some it was like, "let me sign it and get it out of my face." When I finally got up to Smitty, he signed the picture, I asked how his leg was doing and he said something like pretty good, and I think I told him he was my favorite player and I hope he comes back 100% and makes the pro bowl.
The exchange was still awkward and it felt like Smitty was just responding because he had to. I almost wanted to apologize and ask to start over, lol.
Over the years, I've told the stories to friends, some of which were college/pro athletes and they thought it was hilarious. I also met a guy while at school at UNC who went to church with Smitty and he told me he always seemed really cool and fairly warm/approachable.
I think of two things, 1) He has matured a lot over the years so even if someone approached him like I did years ago, his reaction would probably be a little less cold now than it was then and 2) A lot of it depends on the environment and whether the interaction is genuine/organic.
Being that you are going to his charity event, something which greatly demonstrates how selfless and mature he has become since years ago, I definitely think you will have a much better encounter. I'm sure he'll appreciate your selflessness and efforts as well. Just be natural, don't come off as a fandom indulging douche and I think you'll come out of it happy. Helping with his charity seems like a great way to meet him on grounds of mutual respect.