Should I just by a round trip ticket from Osaka to Tokyo for the 4 of us instead of buying 4 JR Rail passes? The Suica card will be sufficient for travel between Osaka and Kyoto but can I use it to get around Tokyo? Perhaps to Hakone for a onsen visit?
I would say Suica. I had a Suica card and could use it in Kansai area without a problem. But you cannot use the Suica card for Shinkansen train. For the other purpose, Suica was useful!
I guess Japan Rail Pass was valid only for JR trains. In Tokyo and Osaka, there are other train lines and busses to get around the city easily such as Metro. If you are planning to move around a lot in Osaka and Tokyo, maybe just purchasing normal Shinkansen ticket might be easier. It will depend on your itinerary.
As for the Suica card, you can use it within Tokyo and to Hakone as well.