Thank You for your reply

My sister, her husband and their friends are both traveling to and from YYZ. I am not sure if they are booked on the same airline. I know they are staying at different hotels. We will probably try to arrange to go the the airport the day of departure together.

My husband and I are traveling to and from LAX.

If I am reading your explanation correctly, I won't have to clear security twice? ( we usually drive to Las Vegas, so I am completely unfamiliar with the airport)