Also, with your grand-daughter living in house, she will be counted in ratios (depending on her age). Is three children enough to cover your current wage?

I would look at transport situation. If you can fix that, it will make big difference. Maybe I misunderstanding, but makes no sense for your husband to pick up son's car and finish at 7pm and wait around until 8pm for son to go home together. What point of getting car at lunchtime to then kill time? Might as well leave son's car where it is, make his way to son's work (he has an hour) and then come home together, or wait around near work for an hour and son pick up husband.