Problem was that the S'ona were dying
Probably becuase they were using crappy non-federation medical tech, just switch over to federation medical technology. It kept McCoy alive so it should keep them alive long enough to figure out how to make their own magic youth radiation.
As for the partial claim thing, thats a dispute they need to work out with their parents, since the federation is around they could possibly mediate it. I mean the Ba'ku didn't have a problem taking them back at the end, the Son'a seemed to be the only bitter ones there.