I used Tony the Limo King

for transportation. Here's what I'll say about the service: if you got a kick out of the original opening of Aladdin, you'll love Tony. Make sure you get his quote in writing, since his prices have a way of changing if you don't.
I got his name and number from the Anaheim tourism bureau website. He charged me $100 round trip. The nice thing was, I didn't have to hassle with parking or driving and they were on my time- whenever I wanted to go, they'd pick me up, whenever I wanted to return, they'd come get me. My boys got a huge kick out of riding in a limo- they'd never been in one before.
When I looked at bus service I found that it would take 2 hours one way to get to the nearest beach. Cabs were more spendy than the limo!
You could rent a car for the day- I think there's a Budget rental right on Harbor. Their "walk away" insurance in CA is only $9.99 a day...so for probably $35 you could get there if you want to drive.
BTW...if you choose Laguna, there's a little shop right on the entrance that rents beach equipment...don't haul your own if you don't want to. There's a play area (swings, slide, etc) for the kids and a wonderful ice cream shop just across the street. We didn't eat there, but there were tons of places to eat, ranging from spendy adults-only places to pizza places.