Gift shop prices are about 40% higher than street, so I make it a point to buy ahead. Several mfrs are now selling sunscreen in 3 oz tubes; you can put several in 3-1-1 baggies for a family. If you use a stick product for your face, that does not count; you can carry sunscreen sticks anywhere. Cans are always too large for carryon.
You can put all the sunscreen you need in checked baggage, but if you are trying to avoid the cost of a checked bag, you might consider ordering some from somewhere like Drugstore.com or
Amazon and having it shipped to your resort. Do the math and figure out what is most cost-effective and convenient for you.
BTW, if you have REALLY fair skin or are on meds that make sun exposure problematic, it is possible to get a scrip from a dermatologist for certain types of sunblock. TSA defines sunblock as a toiletry rather than a medication, so if you have a scrip for OTC sunblock, tape a copy of the scrip to the bottle, and send it through the checkpoint in a bag marked "Medication." (For liquid meds, any size bag is OK, and while technically you don't have to mark the bag, IME it makes your time with TSA go much more smoothly if you do.) Normally, meds of any sort do not require a scrip to be attached to get it though the checkpoint, but sunblock is a special case; if it is not small enough to go in a 3-1-1 baggie, it won't get through without proof of a scrip, because TSA rules do not consider it a "legitimate" medication unless you have a scrip for it.