Tips for Travel to South of Tokyo

This April, we will be traveling Japan beginning and ending at Narita Airport. Our plan is to travel southbound for 2 weeks (April 9 - April 24). I would like to get your advise for the following travel plans.
We arrive to Narita Airport on April 9 at 16:45. We plan on getting the 14-day JR Pass. Since we want to be able to use the JR Pass until the very end of our trip and take the Narita Express getting back to the airport, we won't be able to activate the JR Pass until April 11. Here's our trip plan:
(1) We stay in Tokyo from April 9 to April 11 (2 nights).
(2) On April 11, we go to Otsu and stay from April 11 to April 13 (2 nights). While at Otsu, we plan to go to Kyoto for one of the days.
(3) On April 13, we go to Fukuoka and stay from April 13 to April 16 (3 nights).
(4) On April 16, we go to Kumamoto and stay from April 16 to April 18 (2 nights).
(5) On April 18, we go to Beppu and stay from April 18 to April 20 (2 nights).
(6) On April 20, we go to Okayama and stay from April 20 to April 22 (2 nights).
(7) On April 22, we go to Kamakura and stay from April 22 to April 24 (2 nights).
(8) Finally, on April 24, Kamakura to Tokyo and take the Narita Express back to the airport.
I would love to get advice on this travel and any travel tips would be much appreciated.

Thank You.

You have planned out your trip, you obviously have things you want to do in each location. What actual advice are you after?

ion April 24, Kamakura to Tokyo and take the Narita Express

Have you considered taking the NEX from OFUNA to Narita airport instead of from Tokyo?

You've been to Japan before. Is that why you are virtually omitting Kyoto and Nara? And have you been to Himeji yet? It has some of Japan's very finest.
https://goo.gl/65ZtRi

Three nights is a good chunk of time for Fukuoka. Have you seen some of the sights there before? Such as the Nanzoin Temple, Tochoji, Rakusuien, Canal City, Aburayama, and so on?
http://www.thejapanfaq.com/fukpic.html
http://bit.ly/1KAm8cU

Beppu has its hot springs, but also the Hells Tour, Takasakiyama Monkey Park nearby, and Yufuin is another possibility.
http://bit.ly/2pZ9opz

For Okayama, the Korakuen Garden is one of the nation's traditional Top 3, but don't skip the beautiful Handayama Garden there as well.
https://goo.gl/JQF2bY

Also for Kamakura, you have the chance to see Enoshima as well which has some very good places and scenery.