Legoland is perfect for a 3 year old. Our grand child was too big for some of the rides that fit her younger brother perfectly.

Either one is a good choice barbara, I would pick the Safari or Zoo over Sea World for sure. The reason I mentioned the Zoo is because they have the Children's Zoo and kids can pet the animals. But if they are staying in the North County and going to Lego Land too then the Safari Park is much closer.

If you are in La Jolla, George's at the Cove's Ocean Terrace is the perfect place for a beautiful sunset meal.
https://www.georgesatthecove.com/ocean-terrace