Santa Monica was great when we went. Nothing smelly! No mess either. We were there when the Spirit Film Awards were on and we saw lots of stars leaving the event. We have stayed in central LA at the Mondrian. Check out the pool!!!!

Also Laguna Beach is lovely, beach volleyball court's if they're sporty plus plenty of small shops and restaurants. Huntingdon Beach has a long boardwalk where you can hire bikes, and a pier. We were in Anaheim last November and just hired a car for 24 hours for approx $50 which worked out cheaper than getting Ubers and meant we could be a bit more spontaneous.

@Wildehorses
If your teens are at ALL interested in skateboarding, I would definitely visit the indoor Vans skatepark with them...even if they don't skate, it's very fun to watch the skaters perform miraculous feats from high places🛹🛹🛹.
Not sure if it is still located near Anaheim where@snowgirl1 recommended for the food court place...like SG said, it's not only a food court but also has tonnes of cool shops geared towards teens.

Just thought of another fun off-the -beaten -path thing to do.
If your DC have favourite movies or TV programmes they enjoy they might want to google where the film location is or was and go see the actual place. I do that when I'm in LA sometimes and enjoy it too. Or find out if any are filming at the moment and you can see it live.
I do want to reiterate that unless DC have a favourite celebrity or music star, then you may want to skip the Walk of Fame...there are so many other cool things to do instead.

I second Universal Studios Tours. There is a theme park there, too. And the Warner Bros tour.

And Santa Monica is just a beach town with a bunch of homeless people camped out, and as is the famed Venice Beach.😭 Carmel and Monterrey are much prettier.

And please know that the Pacific Ocean in Calif is very, very cold! ( to me anyway) Around 18° C. Although you said they aren't really into surfing.

On another note...please pack your most casual clothing...Californians tend to dress very slobbily...from billionaires to celebrities...BUT, do bring a pair of trousers along with short pants, light cotton shirts but also a jumper, gilet and a light hooded jacket ( think layers). The days can be on the warm side, then get really windy and chilly in the evenings.

Please check out the safety in San Francisco before you visit...unless they've cleaned it up recently, it's a homeless haven also.
I also second Paso Robles for the wine tours.
Further inland from the coast is where the California Gold Rush happened...you can pan for gold and see the giant sequoia trees...amazing! Biggest trees in the World...you used to be able to drive a vehicle right through one as someone carved a passageway through. Also there is Yosemite National Forest with the tallest trees in the World.

So much to do, but so little time! I would also suggest that if your DC don't enjoy all things nature, to not put those things on your itinerary.
Have a wonderful visit...I'm excited for you!

It is extremely hard to rent a car now because of covid shortages...so you might want to reserve one early. Petrol is around 6 dollars a gallon. The roadways are good but try to choose times to drive when it isn't Rush Hour in the cities.