Yes, kidney stones are possible in toddlers. My son is at high risk for kidney stones. (He went through cancer treatment for Rhabdoid Tumor of the Kidney 3 years ago and his only remaining kidney is having issues with calcium oxalate. He is at high risk for kidney stones. He is followed by a nephrologist and we are working to make sure that the stones never develop). The biggest thing that you can do to try to prevent the stones is to limit the amount of sodium in the diet and make sure that she is getting a lot of water. There is some research that shows lemon juice helps, however there is a still some debate about this suggestion. (My son loves lemonade, so we make it a lot...it can't hurt). We also have been instructed to limit his consumption of strawberries, spinach, nuts, chocolate, and rhubarb. I hope this helps.