Hi Lillian,
First we have to understand why we need to hold a kick off meeting:
It helps team members get to know each other.
It demonstrates the project manager’s authority and leadership skills.
It helps team members understand the project objectives.
It helps stakeholders understand milestones, risks, assumptions, and constraints.
It helps the project manager gain support from all stakeholders.
It provides all attendees with an opportunity to ask questions and get clarity.
It brings all stakeholders to the same platform.
(Source: Pmstudycircle)
For small project, since it is likely that the project team has already be fully assembled in the planning stage, therefore you can start the kick off meeting earlier. For large project, it is likely that you get your full team at the executing stage.