Becky, I have been on many supported rides and I still find that my handlebar bag is wonderful. It holds my meds, cell phone, camera, rain gear, and sunblock...all close at hand. I agree with Tulip that the trunk rack and bag was overkill, though I had one the first trip I went on.

I took three shorts and three shirts just because it can be humid and then stuff does not dry as well. But when you get in to the tent site, you can shower with your clothes on and then take them off for your shower! Then hang the stuff out at your tent and if it is sunny, they will get dry. Let us know if you need any more advice!!