How do I handle the balance between coding things myself and delegating to others?

I'm a L4 at Google, and am TLing a project with 6 other SWEs. I was working on one of the implementation docs, and had to work on a Postmortem incident and its AIs. I sharded off some parts of the implementation to one of the SWEs in the project. I'm back into the project now, and the other SWE is making great progress and I want to let them take it to completion for credits attribution.

I'm confused on whether I should try to do most of the implementation for the designs I write myself or shard it off as other SWEs have a lot less on their plate in December, and early January. Could it be held against me in promo committees that I didn't handle a lot of implementation myself? My org has a high priority on lines of code written, which is causing this confusion.