I don’t think we need to update PEP 8106.
Procedurally, to modify PEP 13:
Changes to this document require at least a two-thirds majority of votes cast in a core team vote which should be open for two weeks.
This does not necessarily have to be part of the SC vote or using Helios, it can be a Discourse poll in the Committers category along with an email for visibility. See How to enact changes to PEP 13 for discussion and agreement on this.
And see Changing PEP 13 to adopt Bloc STAR voting for a similar vote to modify PEP 13 to adopt STAR voting (aside: will come into effect after this SC election).
So it might be easier doing a Discourse poll than using Helios? In any case, it would make sense for the two-week PEP 13 vote to coincide with the two-week SC election vote.
I think we should include an option for the status quo (that is, no defined deadline). If you see two options (2 weeks/1 week) it looks like those are the only options, and there should be a way to actively vote for the status quo.