One fun way to get elementary and middle school students interested in Renaissance art history is to have them paint their own Sistine Chapels by taping paper to the underside of their desks and painting or drawing while lying on their backs. Use this project to lead into a discussion about the work of Michelangelo and other Renaissance artists. They can also read "From the Mixed Up Files of Mrs. Basil E. Frankweiler," which deals with a sculpture that may or may not be by Michelangelo.
Because the Medici family is so central to Renaissance history, you can develop a series of projects around them. As a class, make a Medici family tree. Then have students keep a diary as a member of the family, writing about events in Renaissance Florence from the perspective of a Medici. Students can also interview other students who are playing members of the Medici family to explore themes of patronage, the rising merchant class and power.
Divide students into teams and have them try to imagine the scientific mindset of people in the Renaissance. Have one team gather arguments in support of Galileo's sun-centered Copernican system, and another gather arguments to support the Earth-centered Ptolemaic system it replaced. The students' arguments should be based on Renaissance-era knowledge. This can lead into a discussion of how Galileo's discoveries turned the previous scientific worldview upside down and why the church found his ideas dangerous.
Distribute some contemporary travel brochures for Florence and Venice, and ask students what makes them effective. Then explain to students that they'll be creating travel brochures to Renaissance Florence and Venice, either individually or in small groups. They'll need to gather material through library and Internet research not only on food and festivals, but also on who was in power, the climate and the merchant economy. Have each student or group present one feature of their brochure to the class.