I would not recommend a tort for a beginner, due to the high cost of the animal ($300 minimum) and set-up (enclosure, UV lighting, heat lamp, heat pad). Depending on species, feeding can be tricky and you need experience or else your tort will be malnourished and develop growth deffects (i.e. pyramiding and other bone related problems). You'll need to read up lots before you can pick up a tort. It's not like a guinea pig or pet rat. If your kid likes chelonians, try aquatic turtles, where feeding and husbandry is much easier, but once again the set-up will be high as well, but the animal can be cheaper $50-200 for common aquatic turtles.
Cheers,
JJ