11 day itinerary in march

Hello everyone,
I'm travelling to Japan for the third time with my mom next mid-March. I've already been to Tokyo and Kyoto and seen the major sites, plus Nikko, Kamakura, Kawaguchiko and Nara.
I've only just started planning and this what I've come up with so far. It's the first time I do a more "adventurous" itinerary, so I ask for your advice.

Day 1: we land in Narita at 11am; I was thinking to activate the JR pass right away, use it for the N-EX and make the trip down to Hiroshima (I've looked into flying down, but the first flight is at 5pm and it wouldn't make me spare any time)
Day 2: Miyajima and Hiroshima
Day 3: morning in Hiroshima, then train to Himeji; after visiting the castle, train to Kyoto (I'm thinking about shipping the luggage, would that be easier, rather than having to find a locker in Himeji?)
Day 4-5: Kyoto
Day 6: catch a morning train to Hakone
Day 7: Hakone, some onsen time
Day 8: catch a train to Tokyo (still haven't figured if in the morning or later in the day)
Day 9-11: Tokyo

Does this sound like a doable plan?
I'm still not sure about Hakone, I want to do some onsen experience; an alternative could be Kusatsu onsen from Tokyo, but it seems very out of the way.
Would Kanazawa be worth visiting instead of Kyoto? I'd love to see Kyoto again but also wouldn't mind a new city.
Also, can I make the shinkansen reservation as soon as I arrive in Narita Airport or could the train be booked out?

Thank you very much for your insight. This website and forum is really the best, I couldn't have done my first two trips without!

Re Kanazawa, you could go there and then head to the Noto Peninsula for some onsen time, or stop at one of the onsen towns on the way between Kyoto and Kanazawa.

We've stayed at the Dormy Inn in Kanazawa, which has a nice public bath-not an onsen experience but very pleasant all the same.

Have a wonderful time in Japan!

You will be spending about 5 to 6 hours riding trains on day 1 after your flight. If you really want to go to Hiroshima on the first day, could you fly into KIX or Nagoya?

I will look into the Noto peninsula, thank you!

Regarding the first day and the long train ride, I�fm aware it�fs a lot of travelling. But I already have the flight and I couldn�ft land anywhere other than Narita without either spending a lot or making 2-3 layovers instead of 1. I thought about staying in Tokyo for the first night, but i feel it would be a bit of a waste of time, can�ft usually check in hotels before 3pm, you wander around like a zombie, then freshen up and then it�fs already evening. But i�fm open to suggestions!