If you are not spending any time in or around Tokyo, I don't know how much benefit you would get from a Suica card. You won't be able to use it on Hokkaido.

JR Hokkaido has a 3-day or a 5-day Rail Pass that might be of benefit to you. http://www2.jrhokkaido.co.jp/global/...ss/rail01.html

Many hotels and restaurants and most stores will accept credit cards. That said, I highly recommend getting some cash at HND upon arrival. The ATMs have the best exchange rate but you can also exchange cash at the exchange windows if that won't work for whatever reason. It is perfectly safe to carry cash in Japan and it makes things much easier, using vending machines, making small purchases and paying entrance fees at various attractions. Most temples, museums, castles and such will have a small fee of a few hundred yen. Those typically won't take cards. Likewise, little mom and pop restaurants will probably prefer cash payment. You shouldn't need a lot of cash but even a few thousand yen will come in handy.

Have you seriously considered your visit plans? You are arriving at the start of cherry blossom season and places like Kyoto, Nara, Osaka and even Tokyo will be ablaze in beautiful color. Hokkaido, on the other hand, will still be in the early spring thaw and not nearly so pretty. The best time to visit Hokkaido is May-October or during the dead of winter for the snow festival.

I don't waste time in Hakone so will let others address your questions about that. Likewise transport between HND and NRT. It shouldn't be a problem but my first-hand experience does not include that link.