7 or 14 day rail pass?

Hi, We are in Japan for 14 days and are unsure on what train pass would best suit us and work out best value for money. This is what we are planning on doing.

Day 1. Travel from Narita airport to Koenji
Days 2-3. Stay in Tokyo
Day 4. Travel to Kyoto
Day 5. Stay in Kyoto
Day 6. Travel to Osaka
Days 7-9. Stay in Osaka
Day 10. Travel to Tokyo
Days 11-13. Stay in Tokyo
Day 14. Travel from Koenji to Narita Airport

We were thinking a 7 day pass to cover days 4-10 but wondered if the extra cost of a 14 day pass would be worth getting to cover the trips to and from the airport.

Any advice greatly appreciated, thanks!