Since both of my children have been diagnosed with a gluten-intolerance, and we all follow a mostly "Paleo" lifestyle, most of our food is cooked at home and made from scratch. We eat very, very little processed food, and it's a lot easier to teach the kids to avoid gluten when the only ingredient is the product itself and they help prepare meals.
I'm very lucky that I have one child, my oldest daughter who is almost six, who will eat pretty much everything. My little guy, nearly four, is picky and I swear could sustain himself on organic yogurt, strawberries, and green beans. But one way I've found to get them to try and experiment with new foods is to get them involved in the cooking and making the end product kid-friendly. Here are some things I do with my kids to get them excited to love and eat Real Food and hopefully develop lifelong appreciation and habits.
1) Don't shoo them out of the kitchen when you're cooking (unless safety is an issue). Explain to them what you're doing and how you're doing it. Explain how you're cutting the onion, why you slice the tomato that way, why you peel the cucumber. Tell them what spices you're using and what flavors they give the food. Let them smell the cinnamon and ask them their thoughts. Learning to cook shouldn't be something we keep from children, no matter how young. They listen way more than we give them credit for, even as toddlers.
2) Give them tasks they can "help" with. I give my daughter a butter knife to "cut" up cucumbers for me. I peel them and slice them into sticks and ask her to cut them into cubes. She takes her little cutting board and is so proud of her mushy final product. I started this with her even as young as three with one of those dull kids knives. Kids also love to crack eggs (have them do this in a separate bowl so you can pick out any shells before adding them into your dish), roll meatballs with their hands, mash bananas, and stir batter. Messes are easy to clean up, this time with your kids teaching them important lessons are fleeting. Embrace them.
3) Plate the food in a fun way. As you're getting ready to serve your food, keep reminding them how yummy it's going to be and how they made it themselves and how proud you are. Then put it on the plate in a fun way. Make a face out of carrot sticks and raisins, or make a "taco assembly line." One of my favorite tricks are toothpicks. Put those frilly toothpicks in anything - meatballs, fruit, cheese - and they immediately become fun to eat.
Do you get your kids involved in cooking? What tricks do you use to get them to try new foods?