Sorry the thing at Rudi's did not work out. That said, I think Carnival has been consistent in their no shorts on cruise elegant nights in the upscale restaurants, and I think it is in their doc, but what is done is dine. How they handle it makes all the difference. We travel in groups almost all the time and repeatedly have had some in our group push the envelope even though they understand the rules (regarding shorts). Almost without exception, they were denied sitting but offered the opportunity to go change. Kids are a different topic tho....
Sorry it happened and "flavored" your cruise.