how do I get my kids to be confident to speak in public

Try making your kids do a lot of reading. Try making a simple script for your kids and see if they can read it with confidence. When they are done slowly see if they can byheart the script (make it very short). Once the script is byhearted, next see if they can say it to you without looking or better still make it like a game...I bet they'll start to speak confidently in a few months time. I get my boys to read in the church during mass. I'm glad they no longer feel shy. They are even able to read in school or during family get togethers.