I have somewhat fussy kids and one of my children has bowel issues. I avoid colourings that in the UK, are noted on packaging as harmful, and I use the failsafe list of 'avoid these additives' in most cases. A list of these ingredients is available on 'Fed Up'. I also try and provide as much natural fibre in our diets as I can sometimes I have to be sneaky!
One way I do this is in meaty Bolognaise sauce and Taco beef. I take a small can of red kidney beans and puree them, then add this to the meat when it has browned. I know you would not typically get Red Kidney Beans past super fussy little food inspectors, so wanted to show you a pic of my finished meal ...
If you scrutinise the picture you may identify a mushroom piece or a red fleck of bean but overall the Mushroom sauce really disguises the presence of the beans.
I'd love to hear how this works in your home if you give it a try!