"Anyone who played for the club is obviously part of its history and therefore they'll always be welcome," Duff told BBC Radio Gloucestershire.
"It's an occasion to get former players to come, meet their old mates and introduce them to the new ground."
Duff organised a similar event during the 2009/10 season, shortly after he succeeded the late Peter Vick as club president.
Around 60 people attended the inaugural event, but Duff admits that the hardest part of encouraging former players to the ground is to lure them away from the golf course:
"Some of them now are managing teams and a lot of footballers take the opportunity to play golf," he said.
"I've e-mailed Kenny Norman [who captained the club's FA Vase winning team at Wembley in 1982], Kenny's passed the news around and has even suggested that there could be an opportunity to play a few holes of golf in the morning before the event."
Source: BBC Sport
Source: BBC Sport