No worries. At least he agrees to wear a jacket.
On my last cruise, there were teens with jeans and t-shirts on formal nights but they weren't allowed into the dining rooms for dinner until they at least had an appropriate shirt on.
Mariner-05/06 & 10/09
Oasis Inaugural Cruise-12/09
Monarch-03/10 & 07/10
Mariner; RSS- 10/12
S. Caribbean; Serenade; RC; 12/23/2015-01/04/2016
Australia; Celebrity Solstice 11/27/2016