Your work is so neat and beautiful, and the mint yarn has a great stitch definition. But perhaps the colour combination and the flaring of the shells look a bit like a girl’s dress. For me this would be not important, but if you already know that your son want more “male” clothes, this could be a problem. Often people interpret brownish colours or darker blue tones as more “male”. And perhaps a less lacy stitch pattern would please your son more… But you know him best.
But nevertheless, you did great work and I hope you find a solution.