The stone tribute for Geraldine, Shannon and Shane Newman will be presented at the new Kiln Park retail development behind the Millennium Village on Sunday, January 22.
Wilko shop manager Ms Newman, 51, and her two children, 11 and six, were found dead at their home on Beeston Way on February 2 this year.
Her estranged husband Paul Newman was later discovered dead at cliffs near Anglesey. Police ruled out any other culprits.
Allerton Bywater Parish Council members, Kiln Park developer Priority Space, Millennium Village builder Keepmoat Homes and ward councillors have come together to organise and fund the memorial.
It will be a large stone which includes a plaque, as well as a bench by its side.
Parish councillor Jonny Trayer said: “It’s about bringing the community together really.”
He said the idea was not aimed at bringing back any morbid memories but to provide a lasting tribute to the family.
Mr Trayer said: “At the time there was shock and disbelief. But we came together as well, there was local support.”
He added that although you see those kinds of events on the news you never expect them to happen “on your doorstep”.
The memorial will be presented at 2pm at the back of the Millennium Village off Park Lane.
A ceremony will be led by representatives from St Mary’s Church.
Colleagues of Ms Newman’s from Wilko in Castleford have been invited, as well as with local residents.
There will also be people attending from the Parish Council, Priority Space, Keepmoat Homes and Kippax and Methley ward councillors Mary Harland, James Lewis and Keith Wakefield.
Shannon was a year seven pupil at St Wilfrid’s Catholic High School and Shane attended St Joseph’s Catholic Primary School.
A vigil was held at the Millennium Village where the family lived on the day after they were found.
Flowers, soft toys and balloons were left inside the police cordon as the investigation got underway. One described them as “three special angels”.