Don't think it would be an issue. Maybe I was lucky, but I used the complimentary upgrade to Economy Plus for up to 8 companions for 8 people, booked across 3 or 4 separate confirmation numbers, for LGA-SJD (via IAH). It was a bit of a hassle to corrall everyone's information, but the agents on the Premier line were quite helpful (and pretty patient with me TBH) in making sure I got them all moved.

(not directly related, but generally feel like there wouldn't be an issue boarding in the Premier Access line if I can swing this)