The first step to getting your kids into cooking is to take them food shopping with you. Take them to the grocery store or farmers market, but instead of hurriedly checking things off your list like you usually do, let them help you find the items you're there to buy and tell them what you'll be cooking with them.
Talk to them about the different vegetables and fruits you pass and let them touch them, smell them and if they want to try something, take it home. Give them the opportunity to pick some of the foods that you buy, not all of them of course, but give them two items that they can pick on that trip to try.
Recently my son pointed to a fruit at the grocery store and asked what it was. It was a plum. I realized I had never served them to him since they weren't one of my favorites, but he wanted to try one and, when he did, he loved them. Now plums are a regular request.
A love of fresh ingredients and cooking go hand and hand and a great way to encourage that is by letting them pick out foods and showing them how all of those items at the store come together to make great dishes and meals.