Guy’s cool early opener and Doumbe’s late breakaway goal fired the Dons to within one point of the sixth-placed Cherries in the table.
Milton Keynes dominated the first half and Guy netted his fourth goal of the season to put them ahead after just six minutes. Daniel Powell robbed Marc Pugh of possession near the byline and cut the ball back for Jabo Ibehre, whose scuffed shot was slotted home by Guy.
Frustrated Cherries boss Eddie Howe threw on towering striker Steve Fletcher after just half an hour and he helped the visitors to seize control after the break.
Lyle Taylor dragged a good chance wide from Fletcher’s knock-down and then had a goalbound shot heroically blocked by the lunging O’Hanlon. Fletcher came within a whisker of equalising for Bournemouth in the 82nd minute when he headed Liam Feeney’s cross against the underside of the crossbar.
But Doumbe sealed the win four minutes from the end, racing clear onto Michael McIndoe’s pass to coolly dink the ball over the on-rushing Shwan Jalal.