OP, this is a horrible time, but it will not be true that there is nothing in their lives. This is where
you can truly make a difference!
Many of us have parented children who have been unable to attend school for long stretches at a time and who have also often been in pain and frightened they would grow up unable to ever engage in ordinary life. We have still given them some kind of childhood, we have still given them hope. It can be done!
Your dc do have many advantages here:
they are not (I assume) in physical pain
they can still do a lot of things at home
their friends are all in the same boat and will be eager to engage: they won't have the option to just swan off with more entertaining friends
they are still allowed a certain amount of mobility outside the home
they know that this will have an end- you can plan things for when that happens
These are things I learnt from parenting a child under perhaps rather tougher conditions:
be sympathetic but upbeat: "yes, I know it's tough but you'll manage"
accept that they do need to rant and moan at times, just keep modelling a calm and controlled approach yourself
there will be times when you feel absolutely despondent but you never let them know
distract, distract, distract
make jokes!!!
a schedule seems good here
try to arrange something fun that you wouldn't normally have thought of, but don't go to town on expensive compensations
allow yourself a set time in the day when you acknowledge your pain and despondency and then tell yourself "that's it for today, I'm not thinking more about this until tomorrow, I have a job to do keeping everybody's spirits up"
Also- please get this "paying for the rest of their lives" out of your head! Children have enough stress in their lives without this wretched idea that everything that doesn't work out perfectly is somehow irretrievable!!!
The country is full of people who haven't had the benefit of a full British education, people who have grown up in refugee camps, or simply grown up abroad speaking a different language and following a totally different education system, people who have gone through a period of childhood illness or been in an accident. Often these people do very well in life, because they don't believe that one period of their lives defines them. They're not a specially brave, different kind of person- they're just ordinary people who don't believe it's too late. And they're right!