can you not hide veg in the 'red sauce'? (assume this is tomato based) i know quite a lot of families with children with disabilities of all sorts and sometimes hiding is possible (you'll need to whizz it so that it has no lumps, but sweet veg such as carrots etc is quite easy to hide this way)
given that they like potato/ fish gingers, i'd try getting them to make some home-made fish and potato cakes type thing. you can use whichever fish you can cheap, or even tinned tuna, and they are easy enough to do - quite fun for kids to help make. kids who help make dinner are often more inclined to eat it too. (not sure how your dd is with sensory/ touch - sometimes it can be a good therapy for kids with sensory issues too - dd2 has gone from being unable to touch anything flour/ goop to being ok. ds has always been the opposite and requires a lot of sensory input from his food, so he's a born chef, really. it's still a pita that he has to touch everything on his face before he eats it, but you can't have everything
) mine like to make the fish cakes with peas in too, but again, if you try it a few times without, then maybe you could add peas, sweetcorn or broccoli later.
we've had our share of food issues. dd2 has cerebral palsy and was born with no gag or swallow reflex, so she was ng tube fed, then veeeeeeery slow to be able to manage any texture at all. we had lots of problems with aspiration and regurgitation. she's had a feeding issues trained slt since birth, which has mostly kept me sane, but i sacked the dietician after the first appointment. she is now more or less able to eat a normal diet. ds1 has as-type issues (but odd/adhd - no definitive dx) but again, is now more or less able to manage (there are some things he won't countenance, but perseverance has mostly paid off. at one point he existed on watermelon and cheese for about six months
)
what about lasagne? if they like pasta and red sauce, and are getting on okay with meat, again you can puree carrots etc and hide very successfully in the bolognaise layer?
generally, i think as long as you are happy that they have a reasonably well balanced diet (and you say they are eating meat, some carbs and lots of fruit) then with kids with issues you really don't need to worry too much. so maybe just try and find one acceptable healthier option and lose one of the processed variety - even try and replicate it with no added salt/ preservatives etc?