Alex Young and Kate Walsh
08/23/2007 AT 01:20 PM EDT
is wasting no time on a long engagement.
Less than four months after accepting a proposal
from her real-life McDreamy, movie executive Alex Young, the Grey's Anatomy
actress, 39, is planning to get married over Labor Day weekend.
Young, 36, and Walsh, who stars in the new Grey's
spinoff, Private Practivce
, will wed at California's Ojai Valley Inn & Spa.
In fact, with the help of wedding planner Jo Gartin and her company Love Luck and Angels, the celebration will be a three-day-event.
The festivities will kick off with a rehearsal dinner on Friday, include a pre-wedding meal on Saturday and a sunset ceremony, then wrap up with a post-wedding brunch on Sunday, according to a source.
During the ceremony, the bride will wear a custom made Monique Lhuillier wedding dress, the source says. The Saturday reception will be held outdoors at the inn's Casa Elar, a Spanish-style estate, where the pool will be covered to accommodate the approximately 110 guests.
Among those invited are Grey's
costars Katherine Heigl
and Sara Ramirez.
Says Ramirez about the soon-to-be-newlyweds: "They balance each other out. She laughs all the time when she's texting him. It's really cute."
In June, Walsh told PEOPLE about her whirlwind romance
: "I'm literally living the dream. But you know when you know. I was not expecting it, so it's kind of amazing."