A wonderful park in an old growth redwood grove. This state park is located in Redwood National Park. This national park is a little confusing. The state parks were created first and the national park essentially wraps them all up. You'll find a separate state park for most of the old growth groves with an accompanying campground. Therefore you won't find any specific national park campgrounds.
You will definitely want to stop and spend some time in the visitor center to learn the history of the area. You'll also learn about the plants and wildlife found in the area. There are a few trails and there is a river near the visitor center. The river has a swimming section and we saw several families spending hours down by the river. This park is a good base for exploring the surrounding parks. Or you can hop from park to park in the area like we did. We wouldn't recommend planning to spend a lot of your time in the campground itself, especially with kids (there just isn't that much to entertain you here).
The campground itself was heavily wooded and located close to highway 101. The road noise was dampened by the trees and did die down at night. The sites are well spaced and other than the road noise, the camp felt quiet. The size and levelness of the sites varied pretty dramatically, so check the site details and satellite map.
The bathrooms were pretty disappointing here. They were relatively clean but the fixtures and structures were very dated. The showers here take some sort of token which means you'll need to change quarters to tokens in order to shower. This was the only park in the area that takes tokens (that we saw). The bathrooms down by the river and visitor center were much nicer.
We took a ranger guided tour around the visitor center trail. Our guide was friendly and knowledgeable which made the hour walk very informative. Our visit was in July and the river was pretty calm. I imagine the flow varies quite a bit throughout the year. You will want to watch children playing in the river. The park doesn't have a lot of other activities, but the surrounding area has lots to explore.
There are lots of hikes in the surrounding area. We found AllTrails more helpful than the actual park map but we still recommend picking up an official park map at the visitor center. We especially like the Trillium Falls Trail and the Fern Canyon Trails. Both are pretty easy and around 1 mile each.