Is it a mitzva to live on a Yishuv? I’m a bit afraid of living outside the "green line". Am I putting my children at risk?

It is a mitzva to extend and to strengthen Jewish sovereignty throughout the Land of Israel and to leave no part of the Land uninhabited by Jews- Ramban Sefer HaMitzvot. Someone who lives in a Jewish community in Judea, Samaria or Gaza may, in certain circumstances (is Netanaya or Jerusalem safe?), be exposing himself and his family to greater risks than were he to live outside of Israel or within the "green line". The willingness to assume these risks is, however, not only permissible- it is commendable. It is that "mesirut nefesh" which is necessary to reclaim the Land of Israel for the Jewish People- see the conclusion of Sefer HaKuzari; Shu"t Meil Tzedaka 26.