Irwin, 44, died last Monday after he was pierced in the chest by a stingray's barb while filming a documentary off the far north Queensland coast.
A private funeral service was held for him at Australia Zoo on Saturday, his father Bob Irwin said today.
His best mate and Australia Zoo staff member Wes Mannion said today a memorial service would be held next Tuesday or Wednesday, with Suncorp Stadium a likely venue.
Mr Mannion said few details had been worked out about the memorial service but he hoped it would be fun.
"It's got to be exciting and fun because that's the sort of man he was - he went at 100mile per hour," he said.
Bob Irwin said a weekend service had been held at Australia Zoo for his son around a campfire, the way he would have wanted it.
He said Irwin had always loved "having a yarn" around the campfire.
"It was what he would have wanted and it put some closure to his life," Mr Irwin said.
Irwin's friend and manager John Stainton said the memorial service would be a "celebration" and it was expected that his wife Terri and children Bindi and Bob would attend.
Mr Mannion, who Irwin once saved from a croc attack at Australia Zoo, said there would be no replacing the original Crocodile Hunter.
"I don't think you can ever fill that void," he said. "No, I won't be (the next) Steve, no one can be. I'll remember Steve as my best mate ... he was like my big brother, he was my hero."