Earlier in the semester my Social Studies class participated in a trade fair. This project required each student to bring in several items that they either made, bought or were ready to get rid of. Many students brought in food items, artwork, bracelets or keychains that they made. The purpose of this activity was to see how the trading and bartering system used to work "back in the day". In history people often traded for items that they really needed rather than what they wanted. Although many of the items we brought in as a class weren't necessarily item we had to have it still taught the concept of trade or bartering.
This activity would be great to do with children to demonstrate the technique of trading and bartering. The only concern I would have about doing this with a young class would be how the students gathered their items to trade. You would really have to make sure the parents were involved in the child's selection of items to bring in to class to trade.
Below is a link to another blog about Trade Fairs: