Nice Shogun.
I think you could ride 26 miles tomorrow. But to ease into it, just start adding a little extra distance to one or two of your rides each week. As it gets easier, make all your rides a bit longer but still make a couple of them longer still. You don't necessarily need to do 26 miles in advance of the ride. If you can build up to doing, say 20 miles comfortably, you'll be fine for the event. I don't know your eating and hydration habits, but make sure you eat breakfast before the ride and that you drink about a bottle of water per hour while riding.