Hou ga ii can follow verbs used for giving suggestions and advices. To omoimasu, which means 'I think', often follows this expression, making it sound less assertive. It follows verbs in the ta-form (plain affirmative past) and the nai-form (plain negative past). It can also follow verbs in the dictionary form, but the expression sounds more direct than when it is followed by verbs in the ta-form.
Essential Japanese Grammar, page 194.
From there on the book provides some examples, but no verb in plain negative past form, nakatta-form, is exemplified and, in my little experience, I have never come across such example.
In other words, given the sentence「子供の周りでタバコを吸わない方がいいね」, can we instead say「子供の周りでタバコを吸わなかった方がいいね」? That is, can we use 吸わなかった instead of 吸わない?