(This was a response to a question about the propriety of scripture memorization for young children on the Ambleside Year 0 Yahoo Group.)
Bible memorization is great for young children!
The Bible is clear that it is our responsibility, as parents, to fill our children's lives with scripture. Deuteronomy 6:5-10 says:
5 Love the LORD your God with all your heart and with all your soul and with all your strength. 6 These commandments that I give you today are to be on your hearts. 7 Impress them on your children. Talk about them when you sit at home and when you walk along the road, when you lie down and when you get up. 8 Tie them as symbols on your hands and bind them on your foreheads. 9 Write them on the doorframes of your houses and on your gates.
I can't think of any better way than these verses to express just how much we are to inundate our Children with scripture! Naturally, humans will not tend toward God or the things of God. This is why we must teach our children about God. This includes memorizing scriptures ("tie them... on your hands and bind them on your foreheads"). Passing on the Word of God is one way we prove that we love God.
One thing I've noticed is that Bible memorization actually makes my children think more deeply about God. My 6 year old son often asks me questions about the verses we're memorizing, such as "what does (this particular phrase) mean?" And my 4 year old just thinks and thinks about things without necessarily saying much about them, but I know he is pondering.
We use a lot of motions when we memorize verses. I find this makes the experience more appropriate for young children, as they often learn through motions. We just finished Psalm 8 with my 6 year old and 4 year old. For instance, the first verse went like this:
Lord our Lord (point to sky, since God & Jesus reign in Heaven)
How majestic is your name (spread hands in front of us to show something amazing/majestic)
In all the earth. (make a large round earth shape with our arms)
You have set your glory (big burst above our heads with our hands to show "glory")
Above the heavens (point upwards with both hands)
We do similar motions when we learn hymns, too.
We memorize in the NIV, since that's the most widely used translation. However, we usually read our daily morning Bible reading from the KJV for literary purposes (and we do an easy Bible storybook at night so that even the 2 year old can understand what's going on.)
Charlotte Mason did not recommend large quantities of memorization for the young. She also recommended learning it somewhat differently - just reading and re-reading the passage until the child picked it up. This reading would take place while the child was doing something else - for instance, playing quietly, eating a meal, etc. Many people on this list have tried this method with success. So, this is a method you could try if you like.
As to quantity - we usually learn one verse from a passage every week. Then we add another the following week, and review the part of the passage we've already learned. If they're really short, I'll do 2 a week. We work on this M-F mornings just after breakfast.
We're also learning the children's catechism. So, really, we do Bible verses one week, and switch to catechism the next, and back to Bible verses the following. Catechism requires a lot of explaining about God!
I do like learning a longer passage (such as a short Psalm or the Christmas passage from Luke) because when you take weeks & weeks to learn it, and keep reviewing all the verses, they really stick! If you choose to do shorter verses to start (which would be fine, especially with ages 3-5), just make sure to review often.
Speaking of ages 3-5: You can try memorization at this age, but no need to push it. If they are resistant in any way, you might do more harm than good. Some 3 year olds might not be ready for such a lesson-ish thing. On the other hand, it doesn't hurt to try, since they might enjoy it - especially with the motions. I did not start until my oldest was 5. And I just recently asked my 4 year old to join in saying things out loud (he was just listening before, or running off to play). I feel confident that this is appropriate for both of them - but you really have to know your children to know if requiring this of them is appropriate.