I wouldn't even look at a tri-bike unless your n+1 just goes bat-crazy
. Looking at your bike list, I'd say you're more than adequately equipped to handle the bike leg. I saw more than one mountain bike on knobbies in my race back in May. If you do go with aerobars, I would suggest getting them soon simply to get used to the steering control change and the aero position. It's an amazing feeling crossing that line!