who has custody of 3 grandchildren in california

my son is divorcing his wife but never followed thru w/final judgement. child protective services have taken the 3 children in past because mother was negelgent.son moved in with us w/3 kids,divorce papers say he has full custody &she has supervised visitation however not signed,C.P.S. in Sac co.sent fax to daycare in Eldorado co where kids attend that mother is not be alone with kids if she brings in or picks up to call cops and have children taken to receiving home..Problem:C.P.S. never filed this thru the courts, informal supervision which Eldorado co will not do a curtisey supervision for another county seeings how the father has moved from sac to eldorado co to live with us.now sac cps says they have closed the case & referred to eldorado, so that order he left with the schools to me seems void. We just kicked our son out of the house today as he will not stay away from the mother (who just had abortion friday of another mans baby) but our son felt he needed to take care of her so he farmed out the kids and stayed with her all weekend (again), we felt he was totally using us as he has not paid for anything including food since he moved in 3 months ago nor has he paid his bills so car is on the repo list..what can we do legally?we have left msg w/cps worker in sac as that is where he went with the kids, that he is back in his jurisdiction, mother is homeless living in motel for the time being (paid by her mother)so this is very temporary.and mother will probably be watching the children tomorrow with no supervision from the motel room. I feel we need legal jurisdiction with these kids as it will only be a matter of time till they are taken again by C.P.S. and put back in the receiving home, but right now I have no leg to stand on legally,can't really even take them to the doctors, enroll the 5 yr old in school because I am not their legal guardian..by the way the ages are 1,2,5 yrs old..My son originally moved in because cps told him on a tues in april if he did not get the mother away from the children and get proper day care by friday he was going to take the kids, so we let him move in..
so now the 2 countys are disputing supervision over case,final judgement not filed on divorce,so does that put the kids legally in the custody of both parents??this is by far a mess, and the 5 yr old is in counciling for anger and acting out..go figure..which he wont get to his appt this thurs as no one in sac (family ) will take him, I was suppose to..please give me any advise you can, I know this is complicated and any advise is better than none..thank you Patricia Peterson eloutlaw@cwnet.com P.S. I just retired from law enforcement and belong the a group that re-creates 1860's cowboys and girls, that is where the email address comes from, no I am not an outlaw,20 yrs in law enforcement....just f.y.i.