There are a lot of really great ideas for Bible memorization here. I can think of very little more important than teaching kids God's word.
However, I want to offer an idea. Something that has made a differnce in my ministry for a long time. It always bugged me teaching kids a memory verse every week. Many of the kids would come back every week having memorized their verse and claim their "Bible Bucks." However, these kids couldn't tell me a verse they learned the week before, and definitely not from the week before that. That caused me to ask, "What's the point?" Even more importantly, most of the kids memorized the verses but couldn't tell anyone what it meant or how it applied to their lives. Again, "what's the point?" Even if the game was fun and all the kids memorized it for a week, "what is the point?"
My personal opinion is to use one memory verse for an entire series... maybe for 4 to 5 weeks. Hit the same verse every week, teach the kids what it means... apply it to life situations. Using the verse that often, the kids are more likely to remember it weeks or months later.... maybe it will even stick with them for good. With this method, you may end up with your kids having 6-10 verses cemented in their minds and hearts for life as opposed to having been introduced to 52 separate verese that they neither remember or understand. It's the difference of depth vs. breath. Life change rarely results from breath... but much more likely when depth is the target. Just my opinion and has given me success.
Kenny Conley