If you're concerned that doing something will challenge your integrity, mostly to yourself and the way you see yourself (not really according to the views of others), then simply don't do it. It doesn't necessarily require experience to know if you like it or want it, especially if you already see what your friends are doing as something that you don't really want to partake in. And really, you aren't missing on a whole lot. I don't consider myself straight edge (because why bother?), but I have friends that smoke all the time, and I just don't want to do it. Thats their decision, and that's mine, so I'll spend just as much time with them as I would otherwise; it doesn't really even phase any of us.
Drinking, for me, is an aspect that I'm not really a fan of. Well, drinking to get drunk. You can drink to enjoy it, or for social context, what have you, and not get drunk or really even feel it. That's one of the reason's I don't do any drugs, because each time is meant to have an affect, and well, not for me. But having a nice glass of hennessy, champagne, wine at dinner, or a nice cocktail when talking with friends of old and new, dining, whatever, can be a nice way to go.