My question is: Do I really need booties and open fins, or could I get away with some thick water shoes.
Do yourself a favor. There is a valid reason folks who dive Bonaire's reefs as a general rule use open heeled fins together with the best hard soled boot on their feet. That being, it's required to adequately protect you. Learn from what experienced divers on Bonaire do.
The last thing you want to happen is to have an urchin spine in your foot. Never happened to me, but I'm sure it's far from a pleasant experience.
If you were doing all boats dives, or had shore diving confined to your resort which has a dock, the full foot fin is fine. But, once you start doing shore diving, open heel fins with a good hard soled boot is simply the only way to go. Have fun and be safe!