Brainstorm the types of foods you eat at a picnic with your preschoolers. Help them out if they seem stuck and gently correct them if they list a food not commonly eaten at picnics. Give them some food-themed magazines and help them cut out pictures of picnic foods from the magazine. The children can glue the images to a poster board in a collage. If they don't know what a collage is, explain it to them in the simplest terms. For instance, a collage is a series of pictures glued on a paper in a fun, overlapping way. You can also have the children glue the images to paper plates for a more picnic-appropriate project.
Fill a classic picnic basket with common foods you would take on a picnic. You may want to use toy foods to cut down on the mess. For example, put a toy hamburger and hot dog in the basket, along with bottles of ketchup, mustard and relish. You can put a bottle of water or lemonade and a dessert, such as cookies in the basket as well. One by one, have the preschoolers pick an item out of the basket. Ask them what it is. If they don't know, tell them. Talk about what the food is used for, especially if they pick a condiment like ketchup. You may also consider putting utensils, plates and napkins in the basket.
Give the children small samples of common picnic foods, such as a bite of a hot dog, peanut butter and jelly sandwich or deli sandwich, a taste of mustard or ketchup and a sip of lemonade. You can blindfold the children so that it is truly a blind taste test. Ask each child to describe the taste of the foods. The activity is a great way to introduce children to the five tastes and get them to learn to describe foods. Also ask them about the texture of the food and how it made them feel to eat it. You may have to deal with some picky eaters who are hesitant to try the samples. If that's the case, don't force the foods on them. They may come around when they see their peers sampling and having fun.
Plan your own picnic with a group of preschoolers and let them help you assemble the food. Keep things simple by serving cold sandwiches and have the children help your prepare the desserts. As you bake brownies or cookies or boil the eggs for deviled eggs, ask the children why they think those foods are good for picnics. Reasons may be that they are easy to eat without utensils, they don't make a big mess or they won't spoil very easily.