I have only been on the Conquest but may be able to help....
Try the Library if you have one, will be non-smoking, quiet & very few vistors (nice plush reading chairs & couch if you want to doze off!!!).... I also found that as you exit from the Piano Bar the outside decks had very little trafic & empty lounges (one side is non-smoking & smoking on the other side.....
We also liked to set at a table with an ocean view in the restraunt that has the bufet ( on off hours), the coffe, tea & hot chocalate serving stations were open..... Hope this helps, should be the same for the Destiny...