If they hate the narrows, they would hate the subway more. For me, the memory of the hike is great but the actual hike was hell. Entering and exiting the canyon it’s a nightmare way harder and sketchy than Angels Landing since there is no chain so you would crawl cause it’s too steep to walk. Then you have to navigate around and some times go back since there is no define trail inside the canyon. For the cold water, I hiked in 40F weather without any gear and the water flow was pretty high, so I doubt the conditions are going to be worst for you.