The wedding is formal, so gentlemen should wear dark suits or tuxedos, and ladies should wear long gowns.
The most convenient hotel option is Hilton Garden Inn Atlanta Downtown at 275 Baker Street in Atlanta. Not only will you get a discounted rate, but its rooftop has the eventspace, Ventanas, which is the location of the wedding ceremony and the reception.
Ventanas is located on the rooftop of the the host hotel, Hilton Garden Inn Atlanta Downtown. This hotel has both valet and self-parking options. In addition, there are nearby parking decks adjacent to the venue.