I love this shot, a very natural portrait which portrays the vitality of the two girls.
Catch-lights? Do not get hung up on them, if you look closely you will see the younger girl has one feint one in her left eye. The other eye is too closed to have one, nothing wrong in that.
The depth of field is perfect, portraits of children often benefit from a slightly soft feel. Here the slight difference between the two reinforces the age difference and works extremely well for me.
Their skin tone and lip colour are good too, it tells me that they have been out playing on the beach, running around and enjoying themselves.
I do have one negative point, the younger girl has a slight bogey, once seen never forgotten ha ha,
Quick job to clone that out.
I loke the rest of your portfolio too, you have the eye as they say, keep up the good work.