The most important things you should teach your children are the three G's: who God is; what God has done; what God requires of us. Living a life of faith before our children is of utmost importance. Our responses to trials, what delights our hearts, our service to others - these are the most important things on the curriculum.
Bible - read it, memorize it, talk about it, study it. Understand the history of the Bible and the chronological events of the Old and New Testaments. Even adults don't know about the wanderings in the wilderness, the conquering of the Land, the Judges, the kings, the divided kingdom, the political climate when Israel was caught in the crossfire between Egypt and Assyria, the exile, the return. Without a basic knowledge of Biblical History, it is impossible for the children to understand theology.
Dictionary - use it, refer to it often. Look up words you don't understand and find their derivatives.
A good atlas. Learn the geography of this world. Learn about the lands and the peoples. Follow some missionaries and pray for them. Trevor Johnson has a good blog with links to learn about missions.
Poetry. Start when they are young, reading nursery rhymes. Get them to memorize poetry after they understand the poem thoroughly. Talk about why the poet chose that particular word or phrase. Think of contrast, similes, metaphors, etc. "Oh I have slipped the surly bonds of earth and danced the skies on laughter-silvered wings!"
Read- biographies of great men and women, stories of courage, laughter, joy, sorrow. Get the children to talk about what they are reading. They can do a book report, or draw a picture of their favourite scene or character. They can write a comparison of two characters in a book or from two different books. They can do a diorama or a sculpture, or colour a map of the setting of the story, marking important locations.
Provide pencils, crayons, markers, paint, scissors. Encourage your children to keep a journal and illustrate the events they describe.
Language - Latin, French, Spanish. Latin is intriguing because of the structure and the fact that so many of our English words have Latin roots.
Music. Sing, learn an instrument, do hymn studies. Sing in church. Do special music together.
My goal has always been to instill a sense of awe and gratefulness into our children, and a love of learning, and a willingness to work hard. Teaching good character is important, especially when such teaching equips them to be humble and to rule their own spirits.
Love your children. Pray for them. Spend time with them. Encourage them. Discipline them. Expect the best from them, but don't be too shocked when they stumble. Demonstrate humility of spirit as you acknowledge that you, too, are a sinner in need of grace.