I will be travelling to Japan with my family over the Christmas and New Year period this year. 23 Dec to 5 Jan. We would be there for 14 days and I plan to get a JR Pass for everyone. We would be staying in Tokyo area for the first 3 days and travelling up to Hokkaido via Shinkansen for about 8 days then returning to Tokyo for 3 more days before our departure. In Hokkaido, I will be visiting Hakodate, Otaru, Sapporo and Tomamu. As it will be a peak season for travelling I thought it might be better if I reserve my tickets from Tokyo to Shin Aomori and back via Eki-net. How far in advance can I make my booking thru the website? I believe the English eki-net site allows reservations up to 1 month before travel date. Does the Japanese website allow reservations even earlier than 1 month? I can only understand simple Japanese so I couldn't figure out how early one can book in advance.
Would it be cheaper to get 14 days JR Pass? Or buy individual tickets Tokyo-Sapporo-Tokyo plus a Hokkaido pass?
Also does JR Hokkaido allow for Internet reservations? Or do I have to make reservations when I arrive in Tokyo?