We haven't stayed at this park, but we have been to Clear Lake many times. I-5 to westbound Hwy 20 is a good route. The road is good all the way, but Hwy 20 takes you up over some ridges. Last time I drove that route, the pavement was good, but there are inclines and wide sweeping curves. Another route you might consider is north on Hwy 101 to eastbound Hwy 20. That's a flatter route and the road is all good. The park's website has a construction alert posted for Hwy 29. Check it out before making your reservations.
This time of the year, it will be hot there. The park has no hookups but does have a dump station. Bring a generator to power your AC if you can. But, it looks like a nice park. Check the lake water levels. With our current drought, the water levels could be low.
If you go, let us know how it was and post photos.