What a fun way to participate in a 1/2 IM!

I'd say if your body handles running well, that is doable. Sounds like you're in shape for the rest. Just start where you are comfortable, add 10% distance weekly, taking lots of days off running so you don't stress the body too much. Easy to say, huh?! But seriously, I did 1/2 marathon several years ago and worked up to that fairly quickly once I put my mind to it. The mind is my biggest problem (next to calf cramping!).

Cool goal... give it a try! (or... a tri! I'm SO corny! )