I'm a major advocate of renting dive gear on vacation because it has always worked out well for me, but I do take my own personal gear (mask, fins, exposure suit). Given that your ability to see and have a comfortably fitting mask will have a major impact on your enjoyment of the activity, buying one seems like cheap insurance toward a good time. Especially when you put it up against the overall cost of the vacation. Then you can have it, trust it, and enjoy it for years to come.
For the little bit that you say you're going to do, I suspect you'd get by okay with rental fins. Having your own would likely be more comfortable and again, you'd have them forever, but they might not make a big enough difference to you to justify packing them and lugging them around.
The snorkel? Eh. They neither take up much room in the luggage, nor cost much. If you're ever going to use it again, it's worth buying.
For the space in the luggage that a wetsuit takes up, and the cleaning/drying required once you get it home, I'd probably suck it up and just rent one for the couple dives and try not to think about the fact that other people have peed in it. :speaknoevil: