Fiancée: Howard Stern No Runaway Groom
07/14/2008 AT 05:00 PM EDT
Although, as far as that ever-elusive wedding date is concerned, "Honestly, we haven't figured it out," Beth Ostrosky insisted at Sunday's Hamptons premiere of the movie musical Mama Mia, sponsored by Blackberry.
Still, Ostrosky, who turns 36 on Tuesday, tells Hamptons magazine, "Howard and I were on the lawn the other day, hanging out, saying that we absolutely cannot wait to get married. There are no pre-wedding jitters. It's all excitement and joy."
Inside the magazine, cover girl Ostrosky models a long, white dress by Marquesa (who'll make the price available upon request), another by Nina Runsford ($44,000) and still another by Badgley Mischka ($9,895) – but the bride-to-be says she will wed in Marquesa, whose designer "Georgina Chapman, is actually sketching as we speak," Ostrosky said on the red carpet. "I'm looking at the sketches next week."
As for why this particular designer, Ostrosky tells Hamptons, "I became a fan of Marchesa after I started seeing Sienna Miller wearing their dresses. I've been obsessed ever since."
But when it comes to the wide array of wedding dates, Ostrosky tells PEOPLE, "We're celebrating with our families in August, and then with our friends in October" – with the nuptials to take place sometime between now "and October," she says.
"It's probably just going to be the two of us at City Hall. I'm going to wear the wedding dress for the reception."
In lieu of gifts, the couple will request donations to the Hamptons Wildlife Rescue Center.