Teaching history to your children can be very boring for both of you. In my personal experience, the only time I truly learned any history fact was when the teacher made it fun and engaging for the students--memorization alone will have all your students yawning.
History is most relevant when it is told as a story. Do not teach history facts in a disjointed way.
As you read the stories of history and historians, take notes of important facts. Write these facts as questions and answers, with the question on one side, and the answers on the others. Use these flashcards to test your students on they have learned. By doing this, you are also teaching reading comprehension.
Create a simple board game by making a trail of little boxes on a piece of cardboard. Every 10 or so boxes place a star as is shown in the illustration.
Collect small toys or trinkets from around the house to use as game pieces to mark each player's space. (This game can also be played with an old game board, just change the rules of the game as is discussed in the following steps.
Place the flash cards on a small table with the questions facing up. As each person takes his turn answering questions, he can move forward an appropriate number of spaces. (On the back of the card along with the answer, assign a number of spaces based on how easy the question is.) If a question is answered wrong, the player falls back to the last star.
As each week passes, do not get rid of the previous cards, just mix your new ones in with them. This way you will continue to reinforce the facts you have learned previously.
You can use old game boards instead of making your own.