Sam Slocombe, Connell Rawlinson and Jim O'Brien are out of contract along with Kyle Cameron, Aaron Nemane and Ruben Rodrigues, who have also been offered new deals. Notts County also would lie to sign Jodi Jones on a permanent deal.
Luke Williams said "I'm delighted that we have offered new contracts to Sam, Connell and Jim - all experienced campaigners whose immeasurable contributions aren't completely visible from the stands.
"We would also love to keep Kyle, Aaron, Ruben and Jodi, who have all experienced five seasons' worth of drama in the space of one campaign.
"We're aiming to retain a core of players who have been through the challenges we have faced together and understand the expectations of playing for this club."