4 days in Shibuya

Hope this finds everyone one.

Just wanted to ask what the best option is on travelling around Tokyo during our stay. Our 1st visit last May was awesome but somehow we didn't have enough knowledge about the JR Pass and how it could have saved us money. We stayed in Kyoto first for 4 days, then travelled to Asakusa. Stayed there for another 4 days. We didn't purchase any JR Pass for us, just paid the regular fares whenever we rode the train.

This time, we will stay in Shibuya. Our itinerary would look like this:

Nov 12 - 15, 2015

Day 1: Arrive in Narita Airport at noon, go to Shibuya and check in. Go around Shibuya.
Day 2: Visit 5th Station Mt. Fuji. Maybe until late afternoon before dusk.
Day 3: Go back to Disneyland/Sea. All day until early dinner.
Day 4: Go back to airport at 8am

What is the best option for us if we will consider getting JR Passes? I will travel with my wife and almost-2-year-old daughter, with stroller. How much would it cost for the 3 of us?

Any help will be greatly appreciated.

Thanks and cheers!