I bet you'll be fine to do the century. Don't go out too fast, focus on eating and drinking enough and taking breaks as necessary.
Do you have to choose your route at the start or can you make a decision later in the ride based on how you feel?
Have a great ride. And it sounds like you've taken cycling up with some gusto. Way to go!
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher