When it comes to children, we may often find ourselves short of words and phrases to use to wish them luck. This is mostly because as adults, we are so used to talking and interacting the adult way that we forget how to think from a child's point of view. Having said that, however, children need the most motivation and cheer because of the tender age they are at. Just simple lines and words like "Can't wait to cheer you on!," "I am here for you," "You will kill it," "Today will be tough, but you'll be tougher" and perhaps, a tight hug or some chocolates with these words would be the best way to wish a child good luck!