If you do not want to wear a wedding dress with long sleeves, do not panic. You can always add one Dickie or false sleeves of the Temple under your coat is provided for sealing, or you could settle for change in a white dress, opt for the temple sealing. Brides dress without a temple of the loans still marry in the temple, and have many options for what to wear during the ceremony gasket.
LDS Temple dress rules apply only to loans. The wedding party is not part of the temple sealing ceremony. If the bridesmaids are present at the closing ceremony, they are there only as guests in her bridesmaid dress or a change in their "Sunday Best" dressed for the ceremony.