I have always REALLY enjoyed the restaurant Motif @ the St Regis Monarch Beach in Dana Point.
It can be pricey and its not traditional tapas but more of a "small plates" restaurant. Persian Kabobs, filet diane, vietnamese spring rolls, a variety of different foods and flavors. Also have a great wine selection and offer flights.
And another to avoid...Aire in costa mesa...tapas gone extremely awry. Each item is sized as a tapas but priced as an entree. Impossible to get full and not spend over $50 a person. Go for drinks but eat elsewhere.
What about japanese tapas (izyaka)? The most popular is Honda Ya in Tustin. Go and enjoy some yakitori skewers and lots of small plate specials like the crab shumai and fried octopus. Lots of threads on this place if you do a seach.
Another less traditional option is Oki Doki in costa mesa. Lots of japanese and asian inspired small dishes in addition to larger entrees. Try the shrimp in tomato sauce, beef steak and octopus with green garlic. It has a younger crowd than Honda Ya and a little more energy in the room. I love both equally though.
Since its a 60th Bday, I'm not sure Oki Doki would be appropriate, though the Tatami Room at Honda Ya would be nice if you reserve the whole room (seats about 15 people).