My oldest are 3 & 4 and are very involved in the cooking process. They loved to help me with breakfast - pouring cereal and milk, getting the silverware, toasting bagels & waffles, stirring batter for pancakes or muffins.

My teenage boys (16 and 18) are very able in the kitchen. I am crediting that to a) a natural interest in food and b) encouragement and inclusion when they were younger.  Nowadays one of them is always in the kitchen helping me with supper (at least when they are at home) and they come up with some pretty interesting lunch ideas...steak caesar salad, anyone?

My kids range from 7 to 16 and one or more is always helping in the kitchen.  I use meal preparation to help teach math all through school.  They all love to cook and come up with some wild recipes...lol.  They also all help with dishes and cleaning up.

My sons are grown now, but we used to bake cookies together.  I honestly don't remember having them help a whole lot with meals, but I must have exposed them to cooking enough that they both cook today.  #1 son is married and his wife calls and brags on him when he surprises her with a meal.  He's especially creative with salads.  He surprised her with a fabulous new recipe recently but had to call a friend to ask, "What is a saucepan?" when he was reading the recipe.  We got a kick out of that.  #2 son is in college and lives on his own.  He uses his George Foreman grill to cook chicken quite often, prepares a very healthful diet, and rarely eats out. I guess I did something right!

I must admit that I don't involve my 7-yr old in the kitchen nearly often enough.  When I do, she loves to help bake (cracking the eggs being a big favorite) or anything that involves the hand mixer.  She helps set and clear the table.  Our kitchen is so small that often I just feel like it's easier to be in there by myself to get things done. Plus, I'm often in a rush to get dinner going, etc., after I finish work, it often doesn't even occur to me.  However, your posts are inspiring me to involve her more and branch out to more responsibility. 

Wow - your 7-yr-old cooks ground beef?  I still get nervous letting my 7-yr-old stir things in a hot frying pan.  I watch her arm get too close to that pan edge.

My daughter sometimes helps mix things like the meat for meatloaf, or mixtures for baking.  She always puts the dish soap in the dishwasher and starts it up.  She helps me unload most days.  She brings her dishes to the dishwasher after the meal, and she also is in charge of setting the table at meals.
Once in a while, she has made a meal (like a microwave quesadilla, a microwave egg, yogurt & granola & berries, or cereal).
She loves to crack eggs for me too.

Our rule in the kitchen is, if you help cook or bake, you get to eat one of each ingredient (most of the ingredients, of course - not the raw, dangerous ones).  She likes that rule.
;)

I have always had my kids help in the kitchen!  Now 9 and 12...They make meals on there own, and of course there chore is to clean the kitchen.  My 9 yr old son loves surprising me in the morning with breakfast in bed!  He actually cooks eggs better than me now! 
I say get your kids to help out in the kitchen as early as possible!  You would be surprised at how careful they are with using sharp knives and working with stove and oven.

My 2 girls, soon-to-be 14, and the other just turned 11, do a lot in the kitchen, from washing/drying dishes, to baking items by themselves( we still sometimes taste a small clunp of baking soda or powder because of not mixed properly), to cutting veggies, to cooking meat and breakfast foods....AND sweeping and mopping the floor:)    They need to know who to do that as well as the fun things of cooking!

I started them in the kitchen with me when they were young...making banana bars was (and still is) a favorite...younger dd loved mashing the banana's for them.

I must say that I dont like my kids in the kitchen.  I used to have a helper day (I have 6 kids so it works) but I end up getting frustrated when the other 5 are "starving" and it is taking too long.  I do have them help with dishes and getting the table set and getting drinks for everyone.  I am not good at having them actually help me cook.  I dont bake often (unless I find some recipes with limited sugar and are actually good for them) so when I do bake I let them help stir.

*ducking and waiting for the tomatoes to be thrown*

when they are old enough to not get hurt in the kitchen they are in with me. they help put dishes away and when I am cooking they are on the counter helping me out. some are old enough to stand on stools to help out, but some are still too small and have to sit on the counter. they help measure, pour and mix. then they help set the table.