Don't get me wrong, this looks like a garbage law and I truly hope every California resident is writing or calling their elected representatives to complain about it in specific and excruciating detail, but acting like every nerd's low traffic weblog is putting them at risk of civil action from the State of California strikes me as somewhat hyperbolic and misleading.
(C) An online service, product, or feature with advertisements marketed to children.
(D) An online service, product, or feature that is substantially similar or the same as an online service, product, or feature subject to subparagraph (B).
(E) An online service, product, or feature that has design elements that are known to be of interest to children, including, but not limited to, games, cartoons, music, and celebrities who appeal to children.
Take a look at Michael Dominick's SE blog: https://dominickm.com/
The home page alone violates all of the above.
Lastly, "Business" is not defined here, which is odd since these consumer protection laws always define explicitly who they apply to.
I have extensive experience with P65 and ADA compliance - so vague laws like this one really scare me. The only saving grace here is there is no Citizen Enforcement provision - ie. the AG has to bring suit. Which also means voluntary compliance will be low until the AG makes an example of a few unlucky website operators...
None-the-less, the above applies to all websites unless you want to chance being a test case (and no one does). Child is defined as anyone from 0-18 years old, which is an incredibly broad category.
Ever once talk about music on your blog? Talk about food? Cars? Games? Math? School? Clothing? Programming? TV Shows? Upcoming movies? Flying airplanes?
All of these things are of interest to folks 18 and under too... you don't have to have a blog about Blue's Clues to fall under this deliberately vague, ultra-wide net.