What pass is best?

We are arriving in Narita on Monday evening and staying in Tokyo for 3 nights. We are then heading to Ichinoseki area for 5 nights. On Tuesday 13 Oct we will leave Ichinoseki and thought we might stay in Nikko for 2 - 3 nights before departing Japan from Narita on evening of Friday 16 Oct. We don't know what rail pass would be best. We are thinking about either a 14 day JR pass or a JR East pass. Would we start to use our rail pass straight away for travelling from the airport and in Toyko for sight seeing or only activate for travelling to Iwate prefecture? Also can you upgrade a JR East pass to Green Class? Thanks in advance.