Tier2 dependant extension, can't meet deadline for required doc's

[Minnie Me]

Our 'Tier 2 PBS dependant' visa extension applications (for spouse and teenager) were submitted 3 weeks ago. The '15 working days' deadline for submitting our supporting documents is Friday, 26 Oct.

WHAT HAPPENS IF WE CANNOT SUPPLY THE REQUIRED DOCUMENTS BY THE DEADLINE-TO-SUBMIT DATE (FRIDAY)?

The 2 supporting documents required for the teenager have not come through in the post yet, because of a few unexpected hiccups along the way. Both supporting doc's (including bank card) may possibly arrive by Friday, but also possibly not until next week.

Note: Both spouse and teenager's applications were done together on one online application (you have a choice of either applying separately, or of both applying on dependant parent's application)

So 2 questions:

1) Is it possible or likely that our (or possibly just our teenager's) visa extension application will be denied or cancelled, because we could not get the 2 required supporting documents in to Immigration within the 15 working day limit? We are pretty sure we can have them posted to immigration by Monday, or Tuesday at latest - and even possibly by this Friday (both documents may arrive on Friday)

2) How do you interpret '15 working days'? Because our application was submitted on Sunday 7 Oct. And by my calculation, 15 working days from that date is Friday, 26 October. I wanted to be safe, and post everything by Thursday (tomorrow), 25 Oct, so that the documents would arrive ON the 15th working day (Friday). But I'd like to wait to post now until Friday, just in case the documents come through on Friday. So....based on the '15 working day' stipulation, would POSTING the documents on the 15th working day (Friday) still meet the deadline requirements'?

Thank you