Photos, symbols, newspaper clippings, documents related to ancestor's life
Glue or clear packing tape
First, you must decide which life events you want to be represented in the timeline. I chose to make one for my maternal grandmother (my kids' great-grandmother). I included the main events, such as birth, death, marriage, graduation, and births of children. I also included other events such as immigration and joining the military, which are more unique to her life. You could also include events like moving, receiving sacraments, starting a new job, retirement - it's really up to you and your child. Once you choose the events you are going to include, write each year on the lip of a Styrofoam cup.
I also recommend writing a 1-2 word description of each event on the cup on the opposite side of the date.
For older children, I recommend making cups to represent important events in local or national history that influenced your ancestor's life. For example, the U.S. Coast Guard SPARS would never have been created if WWII hadn't happened, and my grandmother's life would have likely taken a completely different path if she hadn't joined the SPARS and subsequently met her future husband at a USO event. Adding these bigger events to your ancestor's timeline will help children realize the importance of historical events AND it will (hopefully) give them a sense of how their own lives are influenced by the current events of today.