How Old Do You think Ruby, Guido, and Mo are?

Guido seems to be at least a teenager, if not an adult.
Mo could be an adult but he seems to have larger “water kin” than himself, meaning he’s not fully size. So I think he’s still a kid, though he could be a teenager (hard to say).
Ruby seems to me to be at least as old as Littlefoot and Cera, if not older (though it could just be her size and her mature personality.)