"They promised to support and love each other and to make each other laugh," a source tells PEOPLE in this week's cover story. The groom "said he would treasure Blake; she said she would adore him. The whole time they were beaming."
The rustic, romantic festivities – held at Boone Hall Plantation outside Charleston, S.C. – featured whimsical touches, including after-dinner s'mores and a paper-lantern send-off.
The emotional highlight of the evening, however, was when Florence + the Machine singer Florence Welch, a close Lively pal, performed "Somewhere Over the Rainbow."
The Marchesa-clad bride's eyes "started to well up," says the source. "A lot of people started to well up, actually."