Just leave one of the key cards with them, but do NOT turn on valet mode. They need to be able to open both the trunk and the frunk to install the PPF, so valet mode should be disabled.
Just in case you have a third party app such as Stats for Tesla, make sure to shut off the auto lock feature. My Stats for Tesla app will automatically lock the car if it has been parked and unlocked for a couple minutes. Once it locked while I had the car in the PPF place to get a piece of PPF replaced. Oops.