Three years old is still a little challenging. But here are a couple of ideas for you:
I watch kids for a living I let them scramble eggs in the morning with a wisk ! They help me make sandwiches by putting the peanut butter on the bread ! They help me put seasonings on dinner too !
They can learn their counting by putting the fruit into the containers. They can also help get things for you.
Cooking with little ones is a ton of fun .... Make up pasta dough ( flour, egg, maybe a drop of water ) and let them roll it out with a rolling pin. Then they can help stuff their noodles with sauce, cheese, veggies ( if your lucky ) and you roll em up..add extra sauce n cheese on top and bake .... they can make their own pizzas with a bit of help and pretty much anything you just assemble and toss in a baking dish... green bean cassorole is always a favorite and they get to stir ! ( and make a bit of a mess .... it never all seems to stay in the dish ! )
I like to have my son help me measure out ingredients. He truly enjoys it and I get all the help I need when cooking.