I wore mine curly, but mine's not really big or anything. I love love love that you want to keep it natural -- DEFINITELY go for it. In terms of keeping it tame, well... Are you CG? If not, or if you are but are desperate for it to look good, I'd say cheat. Load it up with products, silicons, whatever WORKS. It's one day, after all! You might have a couple of bad hair days immediately after, but I'm sure you won't do any permanent damage! I'd also do a deep condition or oil treatment 1-2 days before, because my hair always looks nice and shiny and non-frizzy immediately after one obviously.

I think most curlies probably worry about big events, especially ones that involve pictures! I know my hair never seems to fall into the same pattern twice, so I never have any idea what it's going to look like on the day.