Full-back Francomb has made seven appearances since arriving from Norwich last month, while Watford centre-half Bennett has played six times, although he is currently injured and will miss Saturday's League Two trip to Plymouth Argyle.
Caretaker boss Simon Bassey told the Dons' official website: "We have extended loan deals for both of them.
"Although Dale is not fit for Saturday, Pim Balkestein could be out for another couple of weeks and Mat Mitchel-King went to hospital for an X-ray on his back.
"That means for two or three weeks we have only Yado Mambo, Will Antwi and Dale as our only three centre-backs.
"We have taken George on loan for another month as he has been a real positive in the last few weeks for us."