Itinerary & using JR Pass

Hi there,

we're planning to go to Japan for 12 days, but majority will stay in Tokyo.
This is my itinerary

Day 1 : Arrive in Narita
Day 2 : Tokyo > Kyoto
Day 3: Kyoto > Tokyo
Day 4 : Tokyo
Day 5 : Mt. Fuji (Yeti Resort) or Gala Yuzawa - day trip
Day 6 : Gihli Museum
Day 7 : Disney
Day 8 - 12 : exploring Tokyo

do you have any suggestion when should I activate the JR Pass.

thank you