In the link below you will find a video telling the story of Thanksgiving in a very basic way for children. It is told from the point of view of Plymouth Rock. Plymouth Rock is said to have been a boulder about fifteen feet long and three feet wide which became a very convinient pier for boats to land, but only with specific tides. It has also gone down in history as the precise boulder on which the Mayflower pilgrims from England, who founded Plymouth colony in 1620, first stepped when disembarking.
The rock that is on display nowadays in Massachusetts is just a portion of the original boulder because it broke in two when Plymouth townspeople try to move it, and also because many people chipped off pieces of it over the years. In 1880 the two pieces rejoined and the date “1620” was carved into the rock.
And here your are the link for the children who may be interested in history and the story of Thanksgiving.