Forward Weston has missed the last four matches with an ankle injury and will continue to remain sidelined as the Gills travel to the Globe Arena looking to further stretch their five-point advantage at the summit of League Two.
Allen has not featured in the last six matches due to his wrist problem but he will hope to get the all-clear ahead of the weekend.
Fellow midfielder Andy Frampton made his welcome return to Martin Allen's matchday 18 for Tuesday's goalless draw at Exeter.
Frampton, who sustained a worrying head injury last month, played the last 30 minutes against the Grecians and could now be pushing to start this weekend.
