It's not that it's too young , it's that I don't know any 50 year olds that have the legs for that. Even if they are slim and toned, peoples knees start looking different at that age, and personally I wouldn't want to draw attention to that by wearing such a youthful, short outfit, as the juxtaposition flags up the difference.
If it was longer, then maybe, or a different , more grown up shape on the shorts, then possibly ,if your legs are good.
Or if you don't give a damn about not being 100% perfect, and you clearly love the outfit and will probably sparkle in it, then go for it.