I loved the San Juan Islands up past Seattle. East Sound, Orcas Island is beautiful and the flight down Puget Sound is fantastic.
Jackson Hole is also good for visiting Yellowstone but April's probably too early for that. Ditto most of Northern Idaho which is very pretty.
If you wanted a target to push for, how about Mt Rushmore. You can fly by or land at Rapid City and get a car. Also check out the Indian version (Crazy Horse) which is nearby. There would be plenty to see on the way too - Sierra Nevadas, all the Arizona and Utah parks, the Rockies, Carhenge (you have to see that - Stonehenge made of grey cars!) etc.
But if you're going Sedona direction from CA, you could do worse than to aim for Santa Fe, NM. It is very pretty round there, especially north towards and past Los Alamos and you could get tempted (like I was) by the jetwarbird place there. Or push on to Carlsbad in SE New Mexico if you are into caves (and these are not just your Wookey Hole sort of caves, they are f**cking huge and so is everything in them - watch for the 2 million bats at sunset).
Only place to avoid is Farmington, NM.