I have an allergic reaction every time I I get on a freeway so this is the route I would take. Little longer than I-5.
https://www.google.com/maps/dir/Reno,+NV/Oakridge,+OR/Coos+Bay,+OR/@43.8003577,-123.1433425,9z/data=!4m35!4m34!1m15!1m1!1s0x809940ae9292a09d:0x40c5c5ce7438f787!2m2!1d-119.8138027!2d39.5296329!3m4!1m2!1d-120.9115449!2d41.3441797!3s0x54cc7a4cf53d5f09:0xef1aa23a112da461!3m4!1m2!1d-121.7129204!2d42.2094707!3s0x54c8d58df8c2f29f:0xb33c0cc403133ddf!1m10!1m1!1s0x54c72e512f94c9ad:0x85928a35c10c9d8f!2m2!1d-122.4617159!2d43.7465124!3m4!1m2!1d-123.4999375!2d44.0734366!3s0x54c10e974c14f9fd:0xdda282b1297fc839!1m5!1m1!1s0x54c3842b1c6c04e1:0x67d7f4c7ddc01229!2m2!1d-124.2178903!2d43.3665007!3e0 The only major grade is on OR 58 Willamette Pass about 6 miles 6%, well marked. Several 45 mph corners.
As Collier Campground is closed as noted, museum is limited. It is a shame as they had great logging displays.
Crater Lake NP for sure. You can drive around the lake or take a bus tour which isn't too bad. I have taken my 35' MH around, road is narrow with rough spots. Diamond Lake is fairly close to the north entrance of the park and the mosquitos always enjoy fresh meat.
There is a casino near Chiloquin
https://klamoyacasino.com/ I can't recall what the stay limit is maybe 3 days. Food is decent. Fuel next door at truck stop. Could day trip up to Crater Lake.
Lots of stuff in the Bend, OR area. Here is one idea.
https://www.visitbend.com/points-interest/newberry-national-volcanic-monument-newberry-caldera/ and
https://www.fs.usda.gov/recarea/deschutes/recarea/?recid=66159If you do decide to go toward Bend you can take US 20 west overs Santiam Pass, 5 miles 6% grade. At bottom of pass, (left turn) follow OR 126 west. DO NOT attempt OR 242 unless you take the toad. The Dee Wright Observatory is worth the drive if you hit one one of the days that you can see into next week.
https://www.fs.usda.gov/recarea/willamette/recarea/?recid=4403Enjoy!