This May we took our kids to San Elijo State Beach for 3 days of camping. (I suggest camp site 59 as it's closest to the beach access.) There are many beaches in San Diego where you can camp; South Carlsbad, San Elijo, Silver Strand near Coronado and in OC there is San Clemente SB or San Mateo Campground near San Onofre SB campground.
Beach Camping is what your kids will remember more than any other vacation. If you let your kids spend their time out doors they will be in their favorite environment and if you want one of the best family time vacations then go camping. It's a little bit more work but you can do things at your own pace and really relax. You will feel like you can unpack and unwind.
These days most families are driving to their vacation destinations. Pack your camping gear in your car and save a lot of money and your kids will have more fun than Disneyland.