Hi Karen,
It sounds like you have a lot of the same criteria for a child's Bible that we do. I also use the NASB and this is the one that I generally read aloud to the children.
I've heard wonderful things about the ESV. Jamie Soles (a friend of ours who sets a lot of the Psalms to music, he writes the music) says, that the ESV flows well and is easy to set to music. When I questioned my father about it's accuracy (my dad is a pastor and reads both Hebrew and Greek), he said that he has been very pleased with the ESV. Anyway, we don't have an ESV yet, but we've memorized a lot of Psalms in ESV (thanks to Jamie Soles cds) and we hope to get one soon.
In our home, as soon as a child begins to read fluently (usually between the age of 4 and 6) we purchase them their own Bible and they begin to read to me from their Bible in addition to their beginning readers. At first it's very slow perhaps not even a full verse a day, but they have all improved quickly.
So far, we've gotten everyone a NKJV and have been happy with that.