Marc Newsham and Dowie were given a half each in a side which also featured Sam Vince, Michael Hollingsworth, Jack Barlow, Niall Doran and Fallah alongside some of United's youth team players and trialists.
In a very open high tempo game, where both sides hit the woodwork, United opened the scoring on 32 minutes when Fallah skipped through the Mansfield defence and his side-footed effort went in off a Mansfield defender.
Mansfield equalised on 89 minutes following a break down from a United attack before Dowie tapped home in the 90th minute to win the match.