We do pretty much every-thing. She will stand at the bench and break or cut up cheese (blunt kids knife), put lettuce on a plate, stir a bowl (scone mix, cake mix etc), tonight she put tomato sauce on our hot dogs and sprinkled cheese on top. She has a go at putting spreads on bread but it can be a bit messy. Yesterday we made scones and she helped use the rolling pin and cut the shapes out. She made her own scone which I cooked, it came out weird but DH ate it with pride - lol.
I think it has made a difference with her wanting to eat the food. I read in a post ages ago about including DD in the cooking and preparation process, and I think they were spot on. She also talks about it and brags about it for days - she really gets quite excited.
DD helped stir some mince the other day. I held the free hand so she didn't touch the hot pan and she held a massive wooden spoon. She actually ate all the mince in her bowl which rarely happens. I'm not sure if it was luck, or if she felt differently because she helped.
DD is 3yr 8 months - DS is 6 months