Been to most of theme park in California. Personally think Lego Land Carlsbad, one hour drive north south from LA is the best place for toddlers.
Small San Francisco, Las Vegas and New York city with all lego blocks. Global historical architectures such as Taj Mahal and Eiffel Tower. They even have small-size water park where all lego blocks are floating around.
This is not a place for who looks for thrill and excitement, but if you are looking for family fun with kids under 7, highly recommend this spot!