If you may believe what their policy says, you shouldn't be that worried.
In fact, even if they'd store your fingerprints and their database would be leaked doesn't mean that everyone can copy your fingerprint in the wild.
Because a biometric device scans a part of your body (e.g finger) but the software used in that device must convert that image to a kind of string, or at least something interpretable for software.
Maybe, device A stores your fingerprint as "abc", and device B as "123".
Yet, that doesn't mean it couldn't be a risk. Fingerprints are still used to identify YOU uniquely and in the future it's only going to be used more. When you travel through airports you give your fingerprint, when you unlock your phone,...
Also, they say that they don't store the actual fingerprint-image. So probably they make-up that string once the first time you enter the theme-park; and when you enter it again the device will again make the same string from the image, and check if it's already in the database. If it is, they have your unique theme-park-ID. Like the process done with hashed-passwords.
Worst case scenario would be that they store your fingerprint and secretly also make a picture of your face with a hidden camera, and they send it to the NSA so Big Brother already knows a bit more about you.
But they probably already have the information that the theme park could offer about you, and more. So don't bother to much about that theme park. :)
What they could do, is with your fingerprint register e.g how much you visit the park or something related, and use that as marketing-strategy somehow.
And if someone really wants to have your fingerprint, they'd just follow you until you throw your StarBucks cup away, or touch a doorknob; to get your fingerprint from there.