Sounds like you have it planned out pretty well.
I'm assuming you know the area well enough to know if there's stores where you can pick up food and drink as you go.
Personally, I would vote for the organized century. But around here, most of the charity rides are actually metric centuries, and there aren't too many 100-mile centuries to choose from.
Riding with a friend would add a lot to it, at least for me, but I've not had that option in a lot of cases.
Regarding the "bail points", all you really need is a cell phone and someone willing to come pick you up if need be, then you don't need any bail points.
One thing that has really helped me the last few years was a good set of lights, because that made the difference between riding all winter or not. If that's something that you'd need later on in the year anyway, consider getting them for the ride.
__________________
"be careful this rando stuff is addictive and dan's the 'pusher'."