There will be a shuttle if you booked through destination weddings that will provide included transportation to and from the resort upon arrival at the airport.
Dressy casual attire for both the welcome party/rehearsal dinner as well as the wedding. Ties are not required. The wedding will be located on the beach so take that into consideration.
Typically during the day the average temperature in April is around 80-85F dropping to a low of 70F at night. Although the wedding is located on the beach this area is shaded during the afternoon so it should not be too hot.