decide collectively to distribute bonuses equitably
using the same principles for assessmnent
You have defined collective objectives within your team and have to assess the performance with regards to these objectives.
What about using the same principles for assessmnent: The whole team has worked and has performed to reach the objectives. You can decide collectively to distribute bonuses equitably.
Invite HRBP to participate to that decision.
You may need also an external point of view to assess your performance: ask feedbacks from your direct customers to justify your self-assessment.
Context: A team has defined collective objectives and having to assess their performance.