I will try to keep this brief....
FIL has a lot of health problems, especially with his heart (he is 70). Over the weekend, he started to struggle to move around, very breathless, dizzy. Today MIL called the doctor, who said he is very seriously ill and needs to be in hospital urgently for treatment. FIL became aggressive and refused to go so they performed an assessment under the MH Act. He has been sectioned, and the last thing we heard, the police were at the house to take him away.
They live 300 miles away in the middle of countryside, miles from the nearest town. Only FIL can drive, MIL is very frail herself and needs help, and BIL lives with them who has learning difficulties. DH really needs to be down there to look after them all. I dread to think how upset MIL is at seeing all this--FIL was apparently very aggressive towards her. In addition to neeeding treatment, the doctor said he was too aggressive to allow him to stay at home. (This is not normal behaviour for FIL) 
I work full-time. DH is a SAHD so we don't have any out-of-school childcare and no friends who could help out. I can't take time off work and I would also struggle to take care of the DD's on my own (I'm disabled.)
The only thing we can think of doing is to take the DD's out of school and DH will take them to stay with my parents for the rest of the week. (My parents only live 10 miles away from PIL). We wouldn't keep them out of school for any longer than the next 4 days.
Is this a reasonable situation to take DC's out of school? We're in Scotland so I think things are a bit different legally than in England. I just can't see any other way around this.