From: Rabbi Moshe Sofer
To: Rabbi Sender Meizlish
When a mourner marries during sheloshim, the seven wedding feast days permit haircutting, bathing, and laundering on the wedding day itself, but subsequent feast days permit only bathing and laundering if both spouses are mourners, and haircutting only if the groom shaved on the wedding day and the bride is not a mourner. The wedding feast does not cancel the sheloshim entirely — unlike a public festival — and the remaining mourning days must be completed after the feast, with the feast days counting toward the thirty.
Source: Shu"t Chasam Sofer YD §348