Charliecat, why not just tell them what they're eating? It would certainly put them off, and hopefully make them think about food in general, and where it all comes from (ie not out of a cardboard box!)
I'm a real believer in children growing up seeing where things come from. Of course in our house we have fishfingers every now and then, but I try to make them up myself in bulk and then freeze them - I can honestly say my DS doesn't know the difference between these and what he has at friends' houses.
One small thing which I'm sure someone else has probably said, is I find if children have had something to do with making their food, they seem to always eat it. DS is only 3 but loves "helping" to put all the ingredients in the bread machine, and to him it's like magic when 4 hours later a loaf of bread comes out.
He also enjoys "helping" me make meatballs, which his little hands are perfect for. Needless to say, any baking we do goes down a treat.
I admit I do like to cook, but even if I didn't I think I'd do these things with DS, as it's a nice way to spend time together, and the only way to get him to try things he'd otherwise refuse to put near his mouth. Yesterday he had kedgeree for tea! I couldn't believe it!