Allen, whose side claimed the npower League Two title at the weekend, will make eight changes to the side that drew 2-2 with AFC Wimbledon on Saturday.
On-loan Southampton goalkeeper Tommy Forecast is set to make his second league start for the club, replacing Stuart Nelson in goal.
Young defenders Mahlon Romeo and Sam Muggleton will make their senior debuts alongside Callum Davies and Andy Frampton in the Gills' back four.
Bradley Dack and Sheffield Wednesday loanee Harry Grant join Charlie Allen and Steven Gregory in midfield, while Myles Weston and Adam Birchall replace Deon Burton and Danny Kedwell up front.
Allen told the club's official website: "We have a combination of some senior and younger players and I have had two hours with John Schofield to get them ready, and there will be no easing off, that's for sure.
"This is a big game for a lot of our players, and we are ready."