More great information - thank you all.

With respect to the discussion about the FS rooms - the floor plan I was sent seems to be a modified version of the Premier Room floor plan on the website. The layout is basically the same, except the bathroom doors are wider (80cm into the bathroom, 82cm into the toilet). The shower is not accessible but the tub is. It is a King and my understanding is that they have just one accessible room and this is it. Based on the measurement I think it will work. My only concern is that the bedroom seems too small to fit a rollaway but, worst case, we can all four squash onto the bed. It does raise the question - is a Japanese King bed comparable to a US King bed?

Thanks for the tip about the Narita Express. I will make sure to buy my ticket from a human! I saw that the 4S offered meet and greet and was wondering whether it was worth it. Might go for it as we will be pretty tired and if the kids are fractious it compounds the difficulty of navigating in a strange airport and a strange city.

I had rejected the Park Hyatt as I had read in a different thread that it was difficult to get to/from.