I can't remember what exit to take. We were on Pacific Coast Highway and just stopping here and there at several beaches such as Huntington (good for surfers), Newport, etc. But when we finally made it to Laguna we liked it better. Less seaweed, etc. People were on the sidewalks oil painting. And there is a small cliff that overlooks the ocean. The kids enjoyed it in the evening when the tides went out. In the evening, there were several tide pools where anemones, starfish, etc. were caught in the rocks. Wear shoes. There was metered parking in the area.
If your kids are looking for a place to shop, you might pick another beach. Most of the shops are up on the cliff and not as readily accessible as shops in other beaches. Beaches such as "muscle beach" have shops near the sand. But that beach isn't necessarily kid friendly. But it is fun for people watching.
I don't know much about the northern beaches. Someone else will have to tell you about those.
