Do the program as written. If you have extra time, go play sports- some flag football or basketball or something.
I would hesitate long and hard before I added more HIIT to WSB. It’s pretty cardio-heavy as it is, and I’m not sure if more is necessarily better.
Walking and sports, however, are really good recovery activities (depending on how aggressive you play). They’re fun, you move in three dimensions (as opposed to straight back and forth) and there’s a wider range of athletic expression (endurance, jumping, etc).
That’s my take.
Are you cutting in the middle of the holidays?
Ouch, man. Good luck.