Tafazolli found the back of the net in the 38th minute and after Vokes was denied by the offsides flag, the former Wolves man headed home in the 82nd minute to give Wycombe a lead to protect for Sunday's second leg.
The Dons, who defeated their hosts three times in the regular season, were reduced to ten men in the second half after Josh McEachran picked up a second yellow card.
Story of the match
While the Dons made the brighter start, it was Wycombe who fashioned the game's first chance on ten minutes. Vokes latched onto a long pass, but he made a mess of his chance and Jamie Cumming saved.
Troy Parrott then came close with his right-footed strike curling just wide of the post.
Twine had another opportunity with just over half an hour gone as from a free-kick, which he drew on a foul from Dominic Gape, but his 30-yarder was denied by David Stockdale.
Vokes then tested Cumming with a header, but the Dons' goalkeeper was equal to the task. He then saw Kesler Hayden head clear a corner that was diverted towards the far corner of the net.
The Chairboys then broke the deadlock seven minutes from halftime when a low cross was blocked by Harry Darling, but the resulting corner from Joe Jacobson was headed in by Tafazoli at the far post.
Wycombe looked to have doubled their advantage as Cumming parried Darryl Horgan's shot, but Vokes scored on the follow-up only to be called for offsides.
Cumming continued to be busy when he saved a left-footed drive from Jordan Obita on 51 minutes.
McEachran was then sent off for a challenge on Josh Scowen on a 50-50 ball.
Daniel Harvie sent in a low cross that Stockdale was forced to tip away and a Wycombe defender was on hand to clear the danger.
After the hosts went close to a second when a shot rattled the crossbar, Tafazolli headed wide from a corner.
Vokes then grabbed the Chairboys’ second when he got his head to a right-wing cross from Garath McCleary to direct his shot off the post.
Man of the match: Sam Vokes
He was unlucky not to have scored in the first half and deservedly got a goal after a performance that saw him be a danger man throughout the whole of the match.