Anaheim is smack dab in the middle of Orange County, where DL is located.
For fun beaches in So Cal, Laguna is great! It has a fun little park right on the beach, fab shops, galleries and restaurants. It's very laid back. I work in Laguna so I'm partial!
Depending on how old they are and how well they swim will determine if you go to a surfing beach like Newport or Huntington.
Depending on time of day, it would take about 30-35 mins to get to any of them.
Great LA Beaches are:
Redondo (grew up there, partial again!) Fun pier, great restaurants, etc.
Santa Monica is great too. The upside to going here is the Prominade, great shops and restaurants, is close by.
Plan on 40-60 mins for LA beaches from Orange County.
Hope this helps! Have a wonderful trip!!
All work and no play makes Lisa a silly girl