For many kids, the only thing you need to get interested in tennis is an excellent racket. That being said, based on where they practice or take classes, you can find that they also require non-marking shoes.
Typically, children are trained in full-size rough courts, where sneakers can leave unwelcome markings or skids in court. It’s worth consulting with the coach or tennis club to see if this is a necessity.
Luckily, top shoe manufacturers all sell non-marking soles, so it’s not especially difficult to choose the perfect pair.