I can only answer from my experience. I shipped from costco.com You don't have to be a member to use it but you will pay more if you are not a member. Anyways. I ordered two cases of water at $7 a case (48 bottles-seems like alot but not for a ten day stay), cheez-its, oreos and famous amos cookies. Total was about $40 and no shipping charge. All the snacks are in individual packs and are for us to snack on in the afternoon. I ordered on Saturday and it is due to arrive on 8/20 right to ASMu where we are staying. Your resort will hold it for you until you arrive. It will probably be at bell services. We arrive on the 21st so the timing is perfect.
You can also ship stuff down to yourself or use staples or gardengrocer.
HTH