12 days trip advice

Dear JRPass Expert

We will visit Japan from 21 Dec - 2 Jan, 2014-2015.
It is our first time traveling in Japan, a country that we have always wanted to see. We are trying to see which pass suit us the best, since there are so many alternatives. We have already booked hotel on the two main destination which is Kyoto and Tokyo.

21 dec: Tokyo, arrival from Narita Airport --> we need to get to our Hotel in Kyoto
22 dec: Day trip to Osaka and then back to Kyoto at night.
23 - 26 dec: Stay in Kyoto (maybe some other day trips to nearby places)
27dec: Kyoto --> Tokyo
2jan: Departure from Narita Airport

So basically we need to travel from Narita airport --> Kyoto --> Osaka --> Kyoto --> Tokyo --> Narita airport
So we where wondering if we should purchase the 14-day pass or are there any cheaper options? Also is the railway pass enough for traveling inside Tokyo/Kyoto/Osaka?
We would like to spend the least money as possible on the transportation. Your answer to us is vey appreciated!

Thank you very much for your help!

Best regards,
Lina