Have 3 1/2 days to retrace back to SFO after driving north for 8 days thru Napa / Sonoma, Healdsburg, Eureka. Would appreciate suggestions as to how to best allocate time. We will spend time at Crater Lake (sperate from 3.5 days). Had thought of maybe Lake Tahoe. Appreciate any feedback.

Trip will be early April.

Once you see Crater Lake, Lake Tahoe will be a letdown IMO.
Continue up I-5 to Grants Pass and get on US 199 and head for Crescent City and the Redwood NP area. Continue down the coast on US 101 over the next 3 days. Muir woods would be a good stop before going over the Golden Gate Bridge into San Francisco.

Once you have seen the redwoods south of Crescent City, even if only driving on the Avenue of the Giants, Muir Woods is not a necessary stop. If going down the coast from Crescent City, Ferndale is a nice town to see, and then taking the road via Cape Mendocino to Petrolia from which one can go back to US101 through Humboldt State Park with the magnificent Rockefeller redwood grove (warning: the road between Petrolia and the state park is at times a dirt road). Mendocino (the town) would be a good overnight stop. The Anderson Valley has interesting wineries, or if time permits (I have not figured out the time/mileage), a drive down the coast to Bodega Bay might be in order.

How much of Crater Lake do you expect to see in early April? The rim road, rim visitor center and lodge will all be closed and as the NPS says, The lake is completely invisible about 50% of the time in the winter and early spring. http://www.nps.gov/crla/planyourvisi...conditions.htm

I agree w/ both Michael and Gardyloo. The Redwoods you will have already seen are MUCH superior to Muir Woods. Absolutely no reason to stop there. And in April you won't be able to explore Crater Lake.

And Tahoe is entirely different than Crater Lake - can't compare one to the other nor skip one because you've seen the other.

In April you should be able to explore Tahoe. But it partly depends on the Weather. Sometimes April is almost summer-like, and other times there are wintry storms and chains.

If it was me, and having to plan ahead, I'd stick to the coast. You say you will have visited Napa/Sonoma/Healdsburg/Eureka . . . which sounds like you are skipping the Mendocino/Sonoma/Marin coasts. I'd visit Ft Bragg, Mendocino, Pt Arena, Pt Reyes, Bodega Bay. I'd stay at least one night in either Mendocino or maybe Little River.

http://www.littleriverinn.com/