If this is your first time snorkeling then i would suggest that you rent your gear on the ship for the duration of your cruise. On our last cruise the cost to rent mask, fins and snorkel was about $25.00 per person for the cruise.
We have our own gear, as we like to snorkel a lot. We have our own gear bag for our mask, snorkel, we have to bring fins for my DH as he has a very large, very wide foot and he usually can't find his size to rent. Otherwise we will rent fins on the beach.
I totally agree with the others that if you are going to make the investement into snorkeling go to your local dive shop and get a mask that fits. Nothing worse than getting a bad seal.
FYI - if the men in your life have a moustache, they will need to vaseline it to get a good seal on their mask.