There are some hills but it's hardly like riding in the Rocky Mountains, my wife managed to do 44 miles out there in April at another charity ride that runs on basically the same roads, at that point it was the longest she had ever ridden on a bicycle.
Your Trek hybrid should work fine, it's listed as having a triple. Shoot for the 28 mile ride if you are used to doing 75-90 mins, that will be a sufficient challenge for you.