I was going to join in on the why aren't they cooking until this:
Should've mentioned, sorry. 15yo has fairly severe dyspraxia so we have to watch what she's doing, just in case
So my 9 year old is also dyspraxic, hence his 6 year old brother is actually more able to cook than the 9 year old.
My nine year old can make himself noodles (yes, I hovered over him and the boiling kettle for a long time, as his muscle tone and co-ordination is so bad). He can do sandwiches, and salads (he knows to be very careful with knives). My 6 year old can do toast and scrambled eggs, bake cakes - reading is what holds him back. As a team I think they could actually have a good attempt at a meal.
While this is going on, I think you just need to take it a bit easy. Whilst thinking of things they might be able to do for themselves if they're not going to eat the family dinner. Freeze the family dinners for you, and let them fend for themselves a bit.
Having said that, the 9 year old eats anything, and the 6 year old is extremely fussy. I just go with it to a certain extent. As long as their tummies are full, if the 6 year old has had bread and sweetcorn today, then OK. Tomorrow I'll do something like pasta that he'll eat.
Once he's older, he will take a turn cooking - I was certainly cooking for the family by 12 - then he can cook what he wants for us on those days. The nine year old with dyspraxia we add stuff as he gets older and we judge him able.