Hey Nicole, I wouldn't give up just yet, you're not going to lose too much fitness in 2 weeks providing your training plan up to that point has been fairly regular....especially as you ran 11 miles and felt ready! I'd say (as a forumite!) if you feel better Saturday, go for a very slow run for about 2 miles to check how you feel with a bit of effort. If you still feel okay, then do the Half Marathon. I did Run to the Beat a few years ago and it certainly is one to look forward too.
If on the other hand you don't recover in time...then give it a miss there are other events and you can book it again next year.
Speedy Recovery!
Paul