I was very happy to find your website. I am currently stumped by a book I read as a child (lets say, during the 70s). Generally speaking, the plot is that a group of kids/teenagers take over an island in between Canada and US and create a nation.  The book opens (I think …) with the sister arguing with her brother who is in a band (I think …) and she has red hair (I think … ).  I believe (I think …) the ending does not work out that well for the newly formed nation / the kids, and that there is some “father knows best” sentiment, ultimately.  In any case the bit I am most confident about is the nation / island / US-Canada waters. 

Thank you for any help!