while hank75 is right that Hanoi or/and Da Nang are preferable to Saigon, damage is already done. And because of that I'd follow your own advice and make last minute decision while in Bangkok, if only because your Vietnamese friend . I you were travelling alone I'd advise you to skip Vietnam part altogether if only to sleep better.
I have feeling all will work well.
As for Bangkok part, 7 days is enough to visit all bars , not just GoodBoys and Freshboys. Don't overdo planning and swim with the flow when comes to debaucheries.
By the way 2026 Tet was on Feb 17 so you don't need to worry about that inconvenience