This is a ride with a height requirement that your 5YO won't be able to reach. This won't stop him going on the ride, it just stops him driving alone, or in theory, being in control of the car.
The reason for this is not safety, but because his feet won't be able to reach the accelerator pedal.
You can fix this one of two ways - either you drive (not much fun) or, you sit your child in the driver's seat, then stretch your foot across from the passenger seat and control the pedal, letting your child steer. It's a bit uncomfortbale but works fine, and the child then believes they are actually driving, which is a big thrill.
We did this for our small 6YO and she loved it. She and her bigger sister rated it the best ride in the park (mum and dad thought it the most boring) because they got to steer!