It's usually just my wife and I and we rent a car. Last trip was to the North and the weather was great (same time of year as you, the week before though it rained like crazy) but I had a backup plan for La Rioja.

We stay in small hotels usually in smaller towns and book a couple days ahead.

One option you don't have listed is Andalusia + Morocco. You can catch 20 Euro flights to Marrakech and Fes from Sevilla and Madrid. It ties in very nicely with Southern Spain for that kind of trip. My wife and I invited some friends on a trip a few years back and had no takers until we added Morocco and suddenly we had 8 people who wanted to come. The Ryanair flights from Sevilla to Marrackech and then Fes to Madrid were cheaper than the train from Sevilla to Madrid.

Granada, Cordoba, Sevilla Marrakech, Fes if you want to do something like that.