Should I drop Kyushu to spend more time in Honshu?

Hi r/JapanTravelTips! I'm planning a 21-day trip for September and could use some advice on whether to keep Kyushu or focus on Honshu. I'm travelling with my father (late 50s), and our priorities are religious/architectural/historical sites, nature hikes, and food. Not huge on huge cities. Any advice is greatly appreciated, as this is our first Japan trip.

My dilemma:

– Is Kyushu worth all the extra travel time for just 4 nights? Or would those days be better spent going deeper in Honshu?

– If I keep Kyushu, should I adjust the stops (e.g., skip Beppu for more time in Fukuoka/Yufuin)?

– Any underrated Honshu spots I’m missing?

Here's our current itinerary: Current Plan (Honshu + Kyushu)

Alternative (Honshu-only)

Instead of Kyushu, I could add days to:

• Kyoto
• Nikko (overnight stay instead of a day trip)
• Kurashiki
• Setonaikai bike ride
• More Kiso hiking
• Maybe going through Kanazawa instead?

Thanks in advance for your thoughts!