What I really think matters to God when it comes to teaching little ones...
There are lots of books out there that show the most amazing human beings who weren't textbook feed. They were saturated by fellowship with family & friends, and encouraged to get outside and get dirty. They were given opportunities to feel, touch, see, experience--- be curious about the world.
They were read to a lot. They were free to really experience life, not just hear and test on it. Especially with younger children, this is not the time, in my opinion, to worry about "can they write their name?" "can they count to 20?" blah blah blah. Will they eventually learn that? Sure!
But what a shame to have a naughty brat, who doesn't know their parents or the Lord well, who is lazy when it comes to reading or investigating but excels on paper with A's. What a waste. God wants our children to be fully alive in Him, and for now, you are the closest picture of God to them. You are the closest, most tangible piece of Jesus.
Make their brains go wild with wonder.
Don't shove papers and pencil in front of them yet. They will have the next 20 years to learn that way.
Above all else, I'd suggest you...build Godly character in them [sharing, responsibility, thankfulness, service, etc] and focus on having fun, reading, exploring, and playing.
Two words---Enjoy them.