Your success as an engineering manager relies on your ability to deliver reliably. If people around you do not trust you to do that, you will not succeed.
How to think about planning for an engineering team is a meaty topic I learned about the hard way. In my first role as an engineering manager, I was not new to sprint planning, but I had a fairly limited experience with several philosophies on sprint planning. During my first year leading a team, we weren’t using any particular estimation method, but the deadlines we set were often missed. I was woefully bad at accounting for my team’s delivery, time spent, and velocity.
Even worse, my team suffered from the lack of accountability for our estimations. There was a sense of constantly drowning in work but with no ability to account for the time spent. This led to over-commitment and unreliable date setting on my part, which, combined with a flood of competing priorities, led to more team suffering.
Just remember, you have the power to change your approach. If you are new to this management thing, borrow liberally from your peers. Ask for advice on your team planning. Try things out and see what works for your team.