1) Release everything generated on the weekend into public domain or under a general free licence (LGPL, Creative commons) that for practical purposes let's everyone use what was generated.

2) Draft an agreement which says something along the lines of "anyone in this group is granted a perpetual licence to use the IP generated on the weekend for whatever purpose they see fit"

What you want to avoid doing is granting equity based upon IP created on the weekend, that will just cause you a nightmare down the line. Equity should only be given to people who are making a long term commitment to the project, and use cliffs, etc.

Typically IP only covers code, design, etc. it doesn't cover ideas, so an idea for a pivot wouldn't be protected by IP law regardless of who came up with it or where. If you decide to build a startup based on your pivot idea just don't use any code, designs, etc. from the weekend unless you've got some kind of agreement in place for it.