I would also say 2-4hours, although once one of our bags didn't make it to our room till the next day (we arrived late evening). Keep in mind that you're also not guaranteed a room until check in time anyway (4pm?) and you won't get your bags back until you're checked in. If you'll need swim suits or anything like that, bring it in your bag. You can buy sunscreen there but it's a little more expensive. On our last trip, I bought some TSA travel size bottles (3oz) at the Dollar Tree and filled one of them with some Sunscreen just for the first day which worked out well.
I would also suggest shipping a box ahead to your resort, but since you're leaving tomorrow it's too late for that. Maybe this will help someone else reading this: If you weren't leaving for another week You can ship stuff ahead so it would be waiting for you at the resort when you get there (bell svcs will hold for you until you arrive). Put your name and arrival date (do NOT put the ressie #) on the package.
hth!