Gillingham, the 2010 winners, gave Poole an early scare when Aidan Kirby's thunderous strike came back off the post before Nick Hutchings saved well from Aaron Rodriguez's follow-up effort.
However, Bennett drew first blood in the sixth minute when he fired home from close range after strikes from Jon Davies and Dan Cann had been blocked.
Bennett then saw a rasping drive saved by Gillingham goalkeeper Jamie Beale before another ripsnorter flashed past the upright as the Southern Premier big guns threatened to run riot.
Although Dan Cann's 33rd-minute effort clipped the top of the crossbar, it was a different story after the break as the Western League Premier Division high-fliers grew in confidence.
But after both goalkeepers had been kept busy during an entertaining second period, Bennett swept home Poole's second to complete the scoring four minutes from time.
Dolphins: Hutchings, Dickson, Buck, Dibba, Davis, Lowes, Elliott, Devlin (Turner, h-t), Bennett, Davies (Preston, 55), Cann (Parrett, h-t). Unused sub: Gillespie.