We end up joining 3 families and, as the number of kids with us was quite something, we decided to do this trip for the kids joy. We visited the Junibacken museum, and was splendid.
Very nicely organized and built, details were everywhere, and both kids and adults loved it. The train ride was really nice, and is a experience that highly recommend.
Next time in Stockholm we will spend most likely experiencing the city life again, But I have to say that this was a very nice idea.