The first and most important thing you can do in this vein is to buy a children’s Bible and read it with them. The Bible is confusing enough for adults to understand, so why would we assume children can make sense of it if we only read them one with adult language?
There are some great children’s Bibles available, and they are geared to children of different ages, from toddlers through college students. You can check out this link for suggestions of age-appropriate ones: http://www.growingupcatholic.com/finding-a-bible.html
Pick a story or two to read as a bedtime story in the evenings, or read the children’s version of the Sunday gospel to them. The stories they hear will prompt questions, musings, and reflections that you can share together even as the Bible does the hard work of introducing them to Jesus and his friends and family. Also, don’t worry if you don’t know all the answers to their questions. It’s ok to say or “Hmm, good question. I don’t know. I’ll have to find out” or “Hmm, I wonder about that too. What do you think?”