Are you on Carnival or another line? Carnival allows nice jeans for dinner. Although that is not really appropriate for formal night, you might be able to get away with it. Re. shoes, most people won't even look, especially if you have very dark shoes on. When we took our nephews on a 5 day, they wore nice shirts with tie and nice slacks for formal night, but even I didn't notice what footwear they had on!