Lots of ideas, and I hope a couple of them will work out. I've done a few organized rides back before I retired, (Ride the Rockies,
GRABAAWR and one in Idaho), but cycling with 2000 of new friends and camping out on a football field isn't as appealing as it once was. Here's the list of where I'd like to go:
I did the Katy Trail with a friend two years ago, and it was a blast. Unfortunately, he can't go this year and I'm not having much luck finding a riding companion, and my wife's enthusiasm for being my sag wagon is muted, so I may try riding solo. Western Colorado is at least a couple of days drive from most of these, but fortunately Amtrak stops here.