Race to Wrigley 2023 - Determining my 5k pace. Can I go sub-20:00?

On the eve of the 2023 edition of the "Race to Wrigley" 5k, I am contemplating what my 5k race pace should be. I entered 21:00 for my finishing time on the race's entry form, but don't know if that is accurate. I've been consistently running 20 mpw and walking 20 mpw for a total of 40 "on my feet miles" per week.

Since May, my "long runs" have increased from five mile run/walks to 12 mile end-to-end runs.  In April, I ran a 23:xx 5k on a handful of weeks training and a few weeks later ran a 46:xx 10k. I haven't raced since then.

I would love to go sub-20:00 for the 5k tomorrow, but I am not super confident that I can go that low as I have probably only run one single mile at the necessary pace (6:27/mi) in the last few months.

Option A:

If I really want to go sub-20, I need to be aggressive in the final two miles. So that would mean I would need something like:

6:45, 6:30, 6:15, 5:30 = ~19:59

Option B:

If I run mile 1 at 6:45/mi pace and feel I'm maxed out, I will just hold that pace for miles 2 and 3:

6:45, 6:45, 6:45, 5:30 = ~20:59

In any case, about all I've decided is my opening mile pace. At the mile 1 marker I'll make my decision on whether to speed up and go for a sub-20.

Off to run on Wrigley Field!