I'm from SD and spent a few weeks in LJ every summer with my kids for 10+ years.
There are good tide pools just north of the Scripps Pier at La Jolla Shores beach. You can learn about them at the Birch Aquarium, which is a nice way to spend a couple of hours in the afternoon with the kids.
You can definitely do Disneyland in a day. Do it one of the first days you're there before everyone has adjusted to the time change. Leave around 6:30am, it's an 1 1/2 hour drive.
Personally I don't think a trip to Catalina is worth it with younger kids.
My kids liked the sea cave kayak tour
https://bikeandkayaktours.com/kayak-tours/la-jolla-kayak-tour-caves/?gad_source=1