I only use the fat free noodles too. The full fat ones tend to be pre-fried in palm oil which is a little too full on for little bodies I think. The other problem with the full fat noodles is they can be very high in salt - not good for little kidney's. I will mix veges through the noodles as well as some grated cheese and chicken (cold chicken left over or any other meat we have left over from the previous nights dinner). I think using fat free stuff is OK if it is small doses. Things like fat free milk and other dairy isn't a good idea, nor is artificial sweetener. I think if you balance the meals well enough they make a nice easy alternative.
Mum, 15month boy, 3yr girl