Kyoto to Tokyo on NYE

Hi, we are a family of 4 flying in from Singapore to Tokyo Narita Airport on 27 Dec 2014 and we planned to go straight to Kyoto through the Nozomi/Hikari Shinkansen immediately after we land. We would then leave Kyoto on NYE (31 Dec 2014) to travel back to Tokyo and stay there for a further couple of days.

There are several questions that I would really appreciate your help with:

Firstly, i understand that JR pass are not applicable for Nozomi/Hikari trains. Would we be able to book the Nozomi/Hikari train tickets from overseas or it has to be done over the counter in Japan? Considering that it is within their New Year's period, would it be difficult to secure good seats bearing in mind that we each come with huge luggages.

If I am to purchase the tickets over the counter, would we be able to get tickets for the day?

Secondly, do I purchase the return trip tickets from Kyoto back to Tokyo together with my departure tickets from Tokyo to Kyoto at the same time?

Thirdly, how high are the chances of getting Green Car tickets of Nozomi/Hikari train for both trips if i purchase the tickets on the day I land?

Fourthly, when I purchase the Nozomi/Hikari train tickets, do I have to pay additional fees? (eg. base fee and car seat fees, luaggage fees etc)

Thanks so much for your help!