If you went up I-5 to Mt. Shasta City, you could check out Mt. Shasta before taking the beautiful drive from there out to Eureka at the coast. Castle Crags State Park is before Shasta at Dunsmuir, a beautiful place to stroll in, intersected by the Pacific Crest Trail. Across I-5 from the park is the Sacramento River, perfect for dropping in an inflatable raft and paddles, even if you don’t know what you’re doing, for a bit of whitewater fun. Trinity/Claire Engle Lake is on the way out towards the coast. All that region, the Marble Mountains, Scott River, the Trinity Wilderness, is awesome. I love it up there.