The shopping trip is a great idea, but even so, I found baby things to be more expensive down there. We did buy a package of swimmies and some wipes, but we shipped a box of things for DS.
One note if you decide to ship: be sure to put your planned arrival date on the package and plan to have the package there either the day before or the day of your arrival. Some of the resorts have been a little difficult about storing packages for guests for what they consider a long time.
I did a little math later, and, including the shipping cost and the cost of the items up here (sales and coupons help), I saved quite a bit of money and knew I had the supplies/brands I wanted.
Have a great trip!