Printable Sheets
If you are looking for a simple way to keep preschoolers entertained, consider going online and printing out a set of activity sheets for the class. Popular activity sheets include coloring sheets and connect-the-dots sheets. If you use coloring sheets, consider using color-by-numbers sheets, which tell kids which colors to use by presenting them with a number. For example, it might tell them that everything that has a 1 inside it should be colored blue. They may also color in the picture they create after completing a connect-the-dots sheet.
Goop
Crate a mixture of a cup of corn starch and half a cup of water. You may need to alter these measurements slightly. If you get the mixture right, the resulting substance will act like a solid when pressure is applied to it and act like a liquid when the pressure is released. The mixture is fun to play with because most substances either act like a liquid or a solid, not both. Try slapping the mixture on a plate. It will not splash! Try rolling it into a ball and watch it melt off your hand after you stop rolling. This activity is best done outside, because it can get messy.
Blocks and Shapes
Provide your preschoolers with a variety of different blocks, shapes and connectors. These could include well-known commercial products such as Lego, Duplo or K'nex. They could also include simple colored blocks and balls. Ask the group to be creative and form different shapes and structures. You could also ask them to sort blocks according to shape, size and color. These activities will promote their creativity.
Tag Games
Sometimes it is helpful to have a game handy that will tire out your group of preschoolers in a short amount of time. Getting them to play one of the many incarnations of tag is an effective way to do this. There is the classic game of tag of course, where if you are tagged by "it" you then become "it." Also consider freeze tag, chain tag and some of the other versions of this classic game.