You can also grate or process broccoli, cauli, swede, almost anything and hide it in spag bol. It is also possible to do the same with meatballs and sausagerolls.

take 50/50 beef and pork mince
grate lots of vegetables and mix in

take half and use for bolognese or similar

add egg and breadcrumbs to bind the rest of the mix and use this for meatballs, sausage rolls, burgers etc.

This is very basic and can be altered to suit whatever vegies you are trying to get them to eat.