It might be worth talking to a fishing guide now if the island will be busy that week. Two gentlemen who have provided us great times over the years are Ramon & Severo Guerrero, phone 226-2325, 226-2324 respectively. They are great fishermen and fun to spend a day with; each cooks a wonderful beach picnic with your catch and will send fillets back with you for you or a restaurant to cook for future meals. Either Guerrero will show you a good time. They specialize in reef and flats fishing. Using a Sam's Club AT&T prepaid phone card, you can call them from the US for just under 25 cents per minute.
You can schedule snorkeling trips after you arrive. Our favorite is Alfonse Graniel, L'il Alfonse under "Goods & Services" menu above, phone: 614-5450; 226-3537; great guy & guide, wonderful with people & fish; ask him about other snorkeling sites after you visit Hol Chan & Shark Ray Alley.
Capricorn Restaurant is a nice experience for the Valentine's dinner: wonderful food, open air, right on the beach, small, secluded. Recommend you make reservations as they sell out for special occasions. They have a link via "Goods & Services" above.
We second the suggestion for Moncho's golf carts.