It is easy to get off the track and confuse children while we are trying to witness to them. We should remember that the primary focus of our witnessing is the Lord Jesus Christ.
It is a good idea not to focus in on a church or denomination and don't put down the church that the child normally attends. You may lose the chance of witnessing to them in the future.
Don't shift their focus to themselves. It is easy to make a humorous comment about an abnormal feature of the child. For instance, "My, you'r tall for your age, you must want to be a basket ball player when you grow up." or "Oh, I just love your curly hair." or "You have just got the most beautiful blue eyes." That child will probably hear similar comments from everyone they meet, and get sick of it. They may develop a negative attitude toward God because He made them that way, or they may become puffy with pride as a result.
Try to keep your focus on the Lord Jesus Christ as a person and not on a 'pet' doctrine. It is our relationship with Him that counts and not so much our understanding of certain scriptures.