John C. McGinley gives a 2-carat-plus ring to his "rock" – his yoga teacher girlfriend

When John C. McGinley woke up Saturday morning, the last thing on his mind was presenting at the Creative Arts Emmys later that day. His first order of business: Get engaged.

The Scrubs star, who plays Dr. Perry Cox on the Emmy-nominated show, popped the question to his girlfriend of two and a half years, yoga teacher Nichole Kessler, 34, in Malibu.

“At about 9:30 this morning I asked Nicole to come down to the lower part of the garden with me in Malibu. I wanted to show her some different flower ideas I had. And I had the rock in my pocket,” McGinley, 47, told PEOPLE on the red carpet of the CAEs at L.A. s Shrine Auditorium. “I told her, ‘Sit down here to see the view of the ocean’ – we live in a bird sanctuary – and I said, ‘Will you marry me?’ and I took out the rock.”

“I instantly said yes,” says Kessler, who is also a birthing doula. “And then I think I was speechless for about five minutes after John told me what the diamonds meant. I was just in tears and just beside myself. I’m still beside myself.”

The couple, who live together, first met through McGinley’s son, Max, 9 (with ex-wife Lauren Lambert). “My son walked up to Nicole on the beach and I was throwing the ball for the dogs in the ocean. And, Max went over to this hot blonde behind me and I was just aghast. I was like, Max you get the dogs. I’ll talk to the hot blondes. And, so we switched.” And of course, McGinley says, Max, who has Down syndrome, will be in the wedding in “one way or another.”

The ring – a 2-carat round diamond flanked by two 1-carat diamonds and a couple of smaller baguettes – was designed by Mervin Haan at a downtown L.A. diamond factory. “I wanted it to be a big rock in the middle, which is Nicole because she is the rock in this relationship. And then on either side of that diamond, I put a carat, and that represents me and my son, Max.” The other stones represent the kids to come, McGinley said.

What makes it work? “John makes me laugh,” says Kessler. “He brings strength into my life and he challenges me to be more of a person than I ever thought I could be.” McGinley quips back, “Nicole is a better athlete than me. She’s just flat out better.”

A wedding date has not been set yet. “We haven’t gotten that far,” says Kessler. “It’s still that trembling, oh-my-God-we-got-engaged stage. I don’t have one of those fairytale wedding ideas.”