The bike doesn't really matter that much, but you know that. Of the ones you mention, I'd probably go with the Raleigh International. Because I like them. The Cannondale might be good. I did plenty of 100 mile plus rides on mine BITD. Some people think they are stiff riding, but I never really noticed that. Pick whatever inspires you.
I kind of think anyone can ride a century with no particular training, if they have any rides in their legs at all. I'd say do a couple ~60 milers to prepare, then just go for it. It will probably hurt a bit, or maybe not. Some of it is genetic. If you're naturally more slow twitch than fast twitch in your muscle make up, it's going to be easier. If you are more of a sprinter, it could take a little more prep.
You will need to eat during the ride. If you don't you might get the bonk around the 3 hour mark.