Southern Oregon coast ...Heceta Head south ...maybe drop down 101 far enough to see the north end of the redwoods around Crescent City CA. Coastal trails abound.
Another plus 1 on this. SW Oregon has some grand country. And if they've not been to the BIG tress, it's a win win deal.
Crater Lake in May? BS
Lower in the Cascades, in May? Bring some Deet.
Save the drive, it's just a damned volcano filled with water.