Congrats on getting to do your first tri (and with an amazing group like TNT- I did a marathon with them- what a great experience).
Anyway, I'm a big fan of Sugoi tri shorts. I just love the length (I've got thick stumps for legs), and compression. Most all the major brands will be great- I just like them the best.

Good luck- you HAVE to let us know all about the tri when you get done- and you know we're gonna want pictures.