Hi,
I would recommend something fast, like 2.8 or faster [1.8, 1.4 or 1.2], since some rides are dark. However, most 'faster' lenses are primes [24mm, 35mm & 50mm]. I would probably suggest a zoom f/2.8 fixed lens. Say a 24-70 F/2.8? Always a great walk around lens and if your camera is newer, you probably have decent ISO capabilities, so you can always up the ISO if needed. From my own kit, i would carry a 24-70 F/4 and my 55mm F/1.8; using the 1.8 on darker rides, but not all, as the zoom feature helps, especially since you cant always move your feet when on a ride, lol].
Good luck and Kungaloosh!!