For cruising the Bosphorus, should we just take the ferry? Or sign up for a Yatch Sunset Cruise? Or take a dinner cruise?
Take a Bosphorus cruise, no gimmicks like meals. We enjoyed the views of the city from the water.
I just took a regular ferry, not centered on tourists, but rather locals. It was a great experience to see the view without being forced to go to the Rumeli Fortress (as interesting as that would have been). I too would skip the dinner part, it's best just to concentrate on the views. You should also consider a (local) ferry on the Golden Horn or to the Asia side (Kadikoy, for example), it's not as scenic but still very interesting.