Kathy, we sail on Silversea/Regent and are non smokers (except for rare celebratory cigar, smoked in the Humidor). On Silversea we have not encountered a suite with "stale smoke" smell. We enjoy our balcony for breakfast on occassion and at sailaway's from each port and have yet to experience smoking wafting from other balconies.
Like Olivia, we enjoy SS--we're booked on the newest SS ship--Spirit on the maiden transatlantic in January.

Recommend you give SS try--the Panama canal
cruise sounds great.

Pls see SS's smoking policy as posted
on SS's website below:

SMOKING
For the comfort of all our guests, The Restaurant, indoors at the Terrace Café, Saletta, Le Champagne, Observation Lounge (Silver Shadow and Silver Whisper), the Show Lounge, Card/Conference Room, Library, Spa/Fitness Centre, Internet Point and Gift Shops/Boutiques are smoke-free. Cigarette smoking is permitted in designated areas of The Bar, outside at the Terrace Café, Pool area, Panorama Lounge, Casino Bar and The Humidor (Silver Shadow and Silver Whisper). Cigar and pipe smoking is permitted in designated areas outside at the Terrace Café, The Champagne Room (Silver Cloud and Silver Wind) and in The Humidor (Silver Shadow and Silver Whisper).

At Silversea, the comfort and enjoyment of our guests is paramount. We recognise that some of our guests smoke and others do not. Most areas on our ships are non-smoking. However, in order to promote an onboard atmosphere that satisfies all guests, there are designated smoking tables in the Panorama Lounge and in certain areas on Decks 5 and 6 for cigarette smoking. Cigar and pipe smoking is only permitted in The Humidor and in certain areas on open Decks 5 and 6. Silversea kindly requests that all of our guests observe the non-smoking areas. These requests are made to provide a comfortable living atmosphere for everyone onboard.