We've had some discussions on these before. It really depends on what type you are thinking of, but at age 10, most are better off with a theraband/dynaband (whatever brand name).
This link leads to a blog from Lisa Howell, a respected name in physical therapy in the dance world.
That said, my kid has one. She is someone who had a flatter foot than average. The foot stretcher came later for her. What came first was exercises at home and before and after dance. She did then frequently, mainly with her theraband. She used to keep one in her dance bag, one in her bedroom and one by the TV in the family room. Also exercises with tennis balls and rolling her foot over a bottle. All sorts of things that brought more flexibility and improved how she used her feet and ankles over time. Tennis balls are still always in her dance bag and much cheaper than a foot stretcher.