Wonderful shot, what a capture! I think your estimation of the dolphin's age is quite spot on as fetal folds (those white folds on the side) disappear at around 6 weeks of age in common botlenose dolphins. It does depend on how quickly the baby gets fat though, and also the population; some dolphins in Moray firth, Scotland, still show their folds at a year of age!
its so really impressive and beauyful.
how young they are, they learn surf before they learn to walk
great capture from a hearttouching scene