Karaboomer, I see your situation as fasteddie does ... doesn't sound too bad to me. As long as they get your attention when you get home and they have all that time with you the 3 days you are off. Toto, like Yoda, sleeps if we have to leave her for any reason ... doesn't even use the wee wee pad, eat or anything the whole time we are gone!
When Toto was that age, she slept a lot anyway ... I would certainly try it and who knows, your situation could change where you would have a little more time each day and not have the long hours you currently have 4 days a week. I know how worried you are but, it's amazing how quickly they learn their "human's" routine and since they do have each other, I would certainly wait and see a while longer! Good luck!!