I think if you do some training leading up to the event and make sure you take a day off in the middle of the back to back rides and a day off at the end of the one long mileage day, then take two days off before the tour I think you should be able to do it IF your attitude is a can do attitude, in some of your post the attitude was not that and if you don't have that can do attitude you won't be able to do it which is why I was doubting that you will be able to do it. So several times every day, starting today and leading up to the tour and during the tour say out loud: "I can do this, I will do this, I will finish it".

And I think as others have said, which were great points, is that finding a small group of slower riders to hang with and talk to while riding will make the ride go faster and be less monotonous.