Start with a post mortem of your year - if possible, send these questions to your team ahead of time as homework - it’s nice to let everyone do this reflection on their own, then come together with some thoughts prepared and to discuss.
What you leave this session with: Answer the question, what do we want to take with us from this past year moving forward? What do we want to leave behind?
Some example questions:
What are three things that went well this year?
What were three things that did not go well this year?
What did you enjoy about this past year?
What did we not know how to do this past year?
Do you have any suggestions on how we can improve for next year?