Longhorn isn't too tough of a course (from what I've read, they've made it even 'easier' by taking out hills on the run) so it won't destroy you like maybe Buffalo Springs in Lubbock would. The weather will be nice too in Austin this weekend so it won't add to the recoup. So, you should have a quick recovery. Also, two weeks between IM 70.3 and Rocky Raccoon is plenty of time. With your half training you're where you'd need to be to do a 25k trail run anyways so you may as well extend the conditioning over and do RR. It would be like getting in a 'free' run you didn't really have to train for specifically. Trail running is different, particularly it is much slower (or it is for many), with softer running surfaces, better scenery, and you tend to focus much more on the trail surface than you would on a road. My point is it would be a great change of pace and philosophy. I think it would be the perfect non-tri run, timed just right. You just finished Longhorn so the pressure is off (and you wouldn't have to worry about turning an ankle right before your 70.3). RR is "only" 15.5m/25k so you'd be out there three hours at worst. And trail runners are so much more laid-back and relaxed compared to Type A "Believe the Hype" triathletes. Road shoes are fine for a trail. From what I found at the RR site, it looks like sweet single track, not technical at all. If you want technical in Texas, come up to Dallas for Rockledge - the operative terms being "rock" and "ledge."

I agree with Trisooner, you should do it, and you will love it! Regular shoes are fine. Keep an eye out for roots and rocks but not so much that you forget to look for the trail markers. :)

Sooner is right about trail runners. They are generally mellow, friendly, and helpful. Trail runs are the ONLY races I've ever been in where on an out-and-back course, the elite runners will give you a smile and say something encouraging as you pass each other. Really cool people.

Heck yeah you should go! Even if you were smashed from your HIM...just to go and lollygag would be fun...
DON'T go for a trail run before your race. Trail running , while slower and easier on the legs can produce catastrophic injuries! (wrenched knees, sprained ankles,)
After your race however if you have a chance to get out a few times and run some trail please do...it will give you an idea which way the wind blows off road.
Road shoes fine. Pay attention on the trails because if you look up, you might go down!
Have a blast!
Can't wait to hear about both events...

Give it a shot but take it slowere and definitely watch where you are putting your feet.

If it isn't too technical regular road shoes will do.

You can always get a pair of gaiters to keep the rocks and debris out of your shoe.