I believe they made both a kiddush Hashem and a chillul Hashem.
A kiddush Hashem was made in that they didn’t drive there on Shabbos.
A chillul Hashem was caused by the issurim d’rabbonon which were violated. I do think amira l’akum is an issue; it’s assur to ride a b’heima on Shabbos. The prize money is schar Shabbos. There may be workarounds (e.g. a shtar mechirah) but I haven’t heard such a thing, and at the least it would be maris ayin.
Someone (ZD?) pointed out that the whole idea of involvement in the gambling business is improper. I hear the tayna.
I’ve seen some try to say that shvisas b’hemto is an issue, but I don’t think any melachah was done by the b’heima.
I’m pretty sure Kapusta isn’t too happy that this thread was posted. 🙁