Now, to the nitty gritty - what tasks can kids safely perform in the kitchen? Rinsing.
Rinsing produce, rinsing beans or fruit from a can etc.
Cutting and chopping.
When it comes to knives, I've allowed some (definitely not all) 6th graders to use real knives under my supervision.
Children 3 years old and up may safely use plastic knives from a child's cooking set or sturdy, plastic disposable knives with a rounded point.
Peeling.
I've had Kindergarteners peel cucumbers.
Depending on the quality of the peeler you use, and on the motor skills of the children you work with - peeling soft vegetables and fruit is another task you can plan for for kids to do.
Mixing.
Pretty obvious, but this can be a very cool task as there are many ways to mix things up! You can mix with wooden spoons, plastic forks, wire whisk...
Some things require a thorough mixing (for example pudding), while for other things (like muffins or pancakes) over mixing is a no-no.
Tossing a salad is another way of mixing things.
And stirring a sauce over heat is also a variation.
Have a hand mixer? Fresh whipped cream is so easy to make, and such a fun experience for children to see how the cream turns whipped.
Have a blender? Food processor? Children can take turns measuring ingredients and dumping them in the machine, but usually the coolest thing is pressing the button to blast that kitchen power tool.
Mashing.
With a fork - sturdy plastic ones work well also.
Two favorite, easy, and healthy dishes that involve mashing: guacamole and baba ghanoush.
Squeezing.
Children are excellent at squeezing lemons and limes.
Before slicing the citrus to squeeze, I ask my kids to bruise the lemon/lime by leaning on it, rolling on the table, and even by throwing the fruit on the table - beating it up beforehand makes it easy to thoroughly squeeze.
I've also had kids squeezing the extra water from frozen spinach, using cheese cloth and also using a metal strainer.
Rolling, shaping, flattening, filling, brushing, layering...
pretty self explanatory.
A word about room preparations.
When you are planning a cooking session, consider your work area and plan on how to best use the space that you have, in terms of safety and productivity.
You might have to move things around to optimize the workflow of your cooking area.
For example, at my local Y I cook with K-6th graders in a Community Room that has a small kitchen attached to it.
Before each cooking session, I make sure to 1) clear the floor space by stacking chairs and setting them aside - after all, we normally cook standing up in our kitchens, and taking the chairs away clears the space of clutter (making it safer for all), and 2) split up the tables (that are usually lined up along one side of the room) to increase usable workspace, and arrange the tables around the room to accommodate each station (or team), making sure there are clear paths to safely walk throughout the room.
Lastly, have ingredients, measuring tools, and materials needed for your cooking session on hand.
Know the recipe and know your plan, and you're ready to go!