This quick lab worksheet is a great resource for examining flowers with your class. Simply pull a few random flowers from the school yard or your home before class that day, and have them examine them.
The first page explains some of the major traits and characteristics of flowers to search for. The second page has places to sketch and answer questions about three different flowers. A second copy could be sent home with them if you have them do the first one in teams of 2-4 students.
Great KAGAN exercise in science!