My advice would be to sell now, while the other sister on the Chanote is still alive (once she passes away, things get more complicated).
As LL has said above, the people living in the house have no legal rights, and if the house was sold they would be forced to move toute suite. But if as you say the family have no conflicts at this time, then your wife's idea of 50/50 (or whatever split) is probably the best.
From experience with these type of things, your wife really doesn't want to get involved with family squabbles, because they never work out well.