Being considered creepy is part your doing and part the other person's interpretation. The only thing you can control is what you do. If the other person interprets that you are being creepy, there isn't much you can do about it. But it's better to reduce this by not being creepy on your end.
So how might you do this? Well first of all start with a simple greeting like "hey do you remember me? We were in camp together. How have you been?" Don't put too much stress on this and just think of reconnecting with her like she's just an old friend instead of someone you wanted to be more than friends with. That way, it doesn't send "creepy" messages that you were stalking her or something. Instead just keep the first parts of your conversations really casual. Engage in some Facebook "small talk" and try to put aside the expectation of rekindling any kind of romance or whatever.
Once you guys have established a more familiar relationship via Facebook, you can try hinting a bit on your life love and her love life or you can reminisce your times in camp and slowly lead to the part where you shared a kiss. But don't do this right off the bat or anytime soon because that will come off creepy and overbearing. You have to reconnect first before you can start a spark again is the main key. However if while you guys talk and you discover that she's in a relationship already, maybe it's best that you back off on that.
And hey, what if she doesn't respond to you? Then that's okay too. People drift apart over time (especially since it has been years) so don't put all your expectations too high or else you may be bound for disappointment. You can always find new love if this doesn't work out so don't get angry or too upset. I mean you can be a bit upset but don't let that get carried away. And try not to be angry at all because she has her own feelings and you are not entitled to her liking you.
Anyway, best luck!