Don't be nervous, think of it as an adventure, heck it is! Since your going with other riders it'll be fun! Bring lots of water, high energy snacks, some type of electrolite replacement and sunscreen, reapply frequently, some $$$, and all the other "stuff" one needs to have when spending the day on your bike. Bring a light too, just in case you're out later than planned.
Since you have a rack I would pack one pannier with your stuff and go. I'm going to say take your LHT just because I love to ride mine. Choose the one that's the most comfortable. Give it a good cleaning. There's nothing like starting a trip with a sparkling clean drivetrain, or maybe that's just me! Most of all enjoy the day being on your bike and riding with friends. bikerHen