All three are pretty good, but this would be my recommended order ->
1. Kinky Boots: amazing cast, really fun numbers, and solid entertainment with a good message.
2. Once On This Island: fun material, amazing cast. Lower than Kinky because they're still in previews and I haven't seen the updated version so don't know what to expect.
3. Miss Saigon : solid cast, great numbers, but the material is very heavy handed and serious. The ending is not hopeful or happy (sorta same with Once... but that one is still more bearable). The context is show is Vietnam War which I doubt a 16 year old would be able to relate with much.
Caption: Every so often there was a rare moment of perfect balance when I soared above him.