I prefer a clip-on tuner such as the Snark (pictured below; click for link to purchase) with a large digital display. I have demonstrated in class how I tune the instruments, and will be tuning your child's guitar for the first several weeks of class. However, independent tuning is a skill that needs to be honed throughout the year through much practice.
I will be making a tutorial video about tuning the guitar and ukulele so that both you and your child can do it successfully. If you have any questions, please let me know!