If you are all on the same reservation and in the same room, it is my understanding you can complete the check in for them. At time of check in, you will need their passport number and expiration date. You'll select your boarding time too, and also upload a photo of each of you for security. You'll need a recent photo with a plain background, no other people in the photo and you must remove glasses if you wear them. I tried to upload a photo with glasses and it wouldn't accept it. If I recall correctly, you can put an individual credit card for each person. In addition to above, you need contact info for each, along with an emergency contact (someone not traveling with you). I think that's about it. You have plenty of time to check in once they open it up. Your e-docs for boarding will usually be available about 24 hours from time check in is completed, that was my experience last week.