The event organised by Glasgow Churches Together will take place on 22 December with Scotland's First Minister Nicola Sturgeon expected to attend.
Plans for the event have emerged as a new report found the driver of the lorry repeatedly lied about his medical history before the crash.
Harry Clarke lost consciousness when the truck careered along a busy street in the city centre but the fatal accident inquiry found the accident might have been avoided if Mr Clarke had told the truth about previously blacking out at the wheel.
Sheriff John Beckett QC has made a total of 19 recommendations, including calling on Transport Secretary Patrick McLoughlin to hold a consultation on whether doctors should be given more freedom to report fitness-to-drive concerns directly to the DVLA.
In a written determination, he said: "The most effective measure to prevent such an occurrence would be to seek to avoid drivers becoming incapacitated at the wheel.
"Responsibility in that regard lies with drivers themselves and Driver and Vehicle Licensing Agency (DVLA).
"It may well be that the single most useful outcome of this inquiry would be to raise awareness of the dangers involved in driving if subject to a medical condition which could cause the driver to lose control of a vehicle."
David Wilson, of Digby Brown Solicitors, which represents one of the bereaved families, said: "The determination confirms so much of what the Morton family and others have known for some time. This was an avoidable tragedy.
"Harry Clarke is not an evil person but he did a series of bad things which led to a tragedy. It's really important to the families that this type of accident does not happen again."