St Leonards School board of trustees chairwoman Ceri Warnock said yesterday the ceremony would be ''focused solely on the happiness the children brought and the happy times we shared with them''.
The children's mother, Katharine Webb, had asked children attending the funeral to ''wear very, very bright colours'' as a tribute to Ellen, who was known for her ''quite out-there fashion sense'', she said.
Bradley (9) and Ellen (6) were killed by their father Edward Livingstone last week in the St Leonards home the children shared with Mr Livingstone's estranged wife, Ms Webb.
Miss Warnock thanked Dunedin residents and the wider community for their generosity in making the service possible.
''The kindness has been quite overwhelming,'' she said.
''It's been incredibly moving.''
About 400 people were expected to attend the service at the school at 2pm.
The school was busy yesterday as volunteers prepared for today's service.
''This immeasurable sadness came and settled in our community last week and, at times, it's threatened to overwhelm us, but [during the service] we are going to try and set aside that feeling, if we can. It's something that Katharine has requested,'' she said.
''We are coming together ... to remember the joy the children brought us and their family.''
She shared how the community was coping in the wake of the shootings.
''Everybody has good days and bad days. Some people have taken it much harder than others,'' she said.
''It's really brought the community together. People have been in [to the school] every day talking and supporting people.''
The school's pupils ''appear quite resilient'' despite the tragedy, but a counsellor would be available from Monday for pupils who needed extra support.
School staff, parents and pupils had visited Ms Webb during the week and she had found it ''quite comforting'' being visited by Bradley and Ellen's friends, Miss Warnock said.
She also praised school staff for their efforts in organising the service and said principal Jo Wilson ''has not stopped working'' since it was decided to hold the service at the school.
The public was welcome to attend and pay their respects during the service, she said.
