While in Redding, see if you can take a day trip up to Lassen Volcano NP.
Option 1 is to head straight north. Some great scenery along the boundary between the mountains and desert. Bend is one of our favorite places to explore around in the NW.
North from Redding, stop by Lava Beds NM. The boys will love exploring some of the lava tubes (buy some cheap LED headlamps before you go). Interesting CG right at the NM. Of course from there, you'll want to head north to Crater Lake NP.
To follow up on SteveAE's post, near Bend consider camping at
Newberry Crater National Volcanic Monument, esp. at Paulina Lake and East Lake. These CG's are by lakes right in the crater. The Obsidian Flow is really interesting. Lots of other trails in the Bend area. Visit Lava Lands Visitors center for other ideas, and drive to the top of the Cinder Cone while there. For fishing, there are a number of lakes on the
Cascade Lakes Scenic Byway. A number of NFS CG's along that route.
Further north, there are a number of interesting trails along the
Columbia River Gorge that go up to waterfalls. We camp at Ainsworth SP. Easy access to Portland also.
Further north,
Mt. St. Helens is a real interesting place to visit. A variety of camping opportunities in the area. From there, head up to Mt. Rainier NP. If you continue further north past Seattle, a day trip on the ferry to explore the San Juan Islands is great fun. We camped at Deception Pass NP in that area.
Option 2 would have you heading west to the coast then north. We prefer to camp at the OR SP's along the coast. To explore the redwoods in northern CA, we camp at Harris Beach SP in OR and backtrack into CA.
There are a number of SP's along the coast. Do some research here and pick a couple, then explore up and down the beach from there. Don't miss some of the
lighthouses. The boys will love to explore some of the
tidal pools. Personally, once I got partway north on the coast, I'd pick a route eastward and pick up the Columbia River Gorge and points north as I describe above.
Besides the mountains vs. ocean difference between options 1 and 2, another difference is how much hiking you will find. While we do a lot of walking along the beaches of the coast, we do more hiking if we follow option 1. Of course there's the difference of ocean vs. fresh water fishing.