Ok...why is it that my DW can't say "No".....well...except to me...

This extremely poor family in our town is having major issues and the mother seems to rely very much on my DW. This family consists of a Grandmother, Mother, Father (we thought, but DW thinks the girls called him "uncle"), and two girls ages 5 and 7 all living in a mobile home. The Father (or Uncle) is disabled and home stricken. The mother and grandmother work at McDonald's. I guess that's all they have of a family, we only know them because our DD played on their older daughter's softball team, but their mother calls my DW for all issues.
Anyway, the mother (probably in her mid-30s) just had some type of artery surgery a few weeks ago that caused her to have two cardiac arrests because the artery's collapsed while in the hospital (I'm not a doctor, and heard the medical information 3rd hand, so not sure to accuracy). At that time, my DW had their two girls stay with our DDs for what was suppose to be 1 night for the surgery, but was stretched to 4 nights (school nights no less) due to the complications since the father (or uncle) couldn't watch them and the grandmother was assisting mother at hospital. Well...the mother went back into the emergency room of our small county hospital tonite and they called us to pick the girls up before the ambulance transported the mother to a real hospital. At least my DW told them it had to be just tonite and called their church pastor to try to gather some additional helpers.
I know they are extremely grateful and comforted that their girls can play with our DDs and take their mind off their mother in the hospital, because she does have serious health concerns. But it is concerning that they have no one close to them that can help them and that they call my DW because they know her from our DD's softball team. The mother's health sounds life threatening, so very concerning what options the children and grandmother may have if something were to happen. I know helping them is the right thing to do, but with DW and I both working fulltime jobs (we work opposite schedules so DDs always have a family member available), and with DW working on a PhD, the stress level's already high.
The good news.....we have Rum.