Stafford Reynolds, the Glentoran chairman, has received confirmation that the Edinburgh club will dispatch a strong squad to honour Leeman's ten years' service on Monday, July 14.
The benefit match will take place at The Oval, which has a 15,000 capacity, and offers both clubs the opportunity for vital match practice as part of their pre-season preparations.
The Evening News revealed details of Hearts' invite to Northern Ireland back in April, and Reynolds confirmed that arrangements are almost finalised for an attractive friendly in Leeman's benefit.
"Hearts will play here on the Monday night, the 14th, and then use the ground the following day for training.
"Everything has been agreed and the contracts will be signed by the end of the week," he said.
"I gather there will be a number of their guys travelling over and we're looking forward to having Hearts in this part of the world again. Last time I remember us being in touch with them was when we sold Andy Kirk to them many years ago."
Added Reynolds: "The game takes place over the traditional July 12 holiday weekend here, which I'm sure everyone is familiar with. It should make for a good atmosphere. This will help us prepare for our preliminary round matches in the UEFA Cup.
"We'll be playing opposition above our level so it's an attractive fixture for us and a good test. I believe Hearts intend to use the game as part of their own pre-season preparations. It will be good to have them visit Northern Ireland and hopefully they'll enjoy their stay. Maybe in the future they might consider it as a base for a training camp."
Meanwhile, under-19 players Eddie Mearns and Ross Hamilton will leave Hearts at the end of the month after being told the club will not be renewing their contracts. Mearns, a central midfielder, and Hamilton, a versatile left-back and midfielder, were in the final year of their contracts but have a number of interested clubs ready to make a move.