buckwheat pasta is actually very tasty, bursting with nutty flavours, if some kids can get over the weirdness of pasta being brown with some dark dots, instead of being white, this can easily be a winner.
Italian version of buckwheat pasta is called pizzoccheri
, they are more like thick and shorter tagliatelle. The traditional recipe is the pasta tossed with oodles of melting cheese, garlic butter, potatoes and your choice of vegetables (shredded cabbage or spinach is the traditional selection, which can also be tricky with some picky kids, I have tried it with broccoli, chopped brussel sprouts and mushrooms they are also great, another possible option is courgette/zucchini... let the kids choose the vegetables.), they are so wonderfully rich and tasty (though not particularly "light"...), and well enough covered so you can hardly see the difference of the pasta. It makes a gorgeous dinner especially on a chilly evening. It is well worth a try.
BTW we also have an extraordinarily stubborn, picky 7 year old boy(well, son of my partner who lives with his mother) who should really be growing out of his "little kid fussiness" but showing no sign of it, I would welcome more input as to how to "break" picky children!!