Opinions on my itinerary May 2015

Just booking up my honeymoon trip in May 2015 and wondered whether this looks like a reasonable itinerary:

12-14th Arrive Tokyo early morning stay 3 nights
15th (Activate 2 week JR pass) travel early to Nagano stay night
16-17th travel to Kanazawa 2 nights
18th Travel early Takayama stay night
19th-22nd travel to Kyoto 4 nights
23-24 Hiroshima (stay both nights in Hiroshima and visit Miyajima rather than stay one night in each??)
25th travel early to Mount Koya (recommendations whether to go Via Osaka or Kyoto?) I understand I'll need to get the separate rail ticket/buss pass from Osaka to Mount Koya..spend one night there
26-27th travel to Hakone for 2 nights (best route presumably back via Osaka?)
28th return to Tokyo
29th Depart

I'm assuming the Rail Pass is going to be the best/cheapest option for what we're proposing to do?

Also a quick question re the JR pass, I've noted that people on here are discussing reserving seats for journeys, is this easy to do and how far in advance of each train journey is it required? I was under the impression that the JR pass enabled jumping on and off trains and the flexibility associated with that rather than being tied to a specific train, but also would be nice to have a seat. Not going for the green pass, just the basic pass.

Thanks!

As far as the pass is concerned, you can do both jump on and off trains (provided there are seats available in unreserved cars) and also reserve and "lock down" a specific seat on a specific train. If you like the fly-by-the-seat-of-your-pants travel, then, by all means, go for it! I'm more of a planner who lays out everything pretty much in advance and takes the first train out and spends a day and night in one place to scope it out, then repeat the same the following day. I also spend a few days in places I have friends and use them as bases for day trips. I also like to make sure I have the train seats I want.

The JR Pass offers the flexibility of both ways to travel.

You sit on a reservation or a non reservation seat.

During peak periods E.g. Sakura or Momiji in Kansai, most shinkansens are booked out. So reserving early is good. Of course, if you were to take the shinkansen at its starting station, where there are fewer people, getting an unreserved seat is easier.

Reservations is for the comfort of knowing you have a seat. Though, truth be told, most of time there are empty seats in the unreserved carriage. If you feel lucky or am not travelling during peak seasons, you can afford the flexibility of having non reserved seatings. Just jump trains so to speak.

For myself, I reserve all my train tickets that I am certain of.