First, let me thank everyone who replied to my earlier post "Kyushu for first visit to Japan?"
We have booked tickets and will arrive in Fukuoka on the morning of Tuesday, May 13 and will be in Japan until Monday May 26, when we will depart from Fukuoka. This is well after Golden week so I assume the tourist sites will not be exceptionally crowded.
I have some rough ideas about our itinerary: first night in Fukuoka, one or two nights in Yufuin or Beppu, Mount Aso, perhaps Kumamoto and definitely Nagasaki.
We are a couple in our early 50s, reasonably fit. We want (some) comfort but don't need luxury. We like a mix of city experiences (architecture, museums, etc) and rural / natural scenery sights.
Some questions to the experienced Kyushu visitors on this forum:
1) keeping in mind that this will be our first visit to Japan, what would be your preferred itinerary? (for a 13 day/night trip);
2) any recommendations for hotels / ryokans?;
3) should we get a Kyushu rail pass or is it more cost-efficient to buy individual tickets?
4) I still need to buy a guide book, is there any guide book (or website) that you particularly like?
5) any other recommendations for our trip?

Thanks in advance for any replies!