I believe you'll need separate ADRs for them. If you arrive early for your ADR you can ask to be seated together but there's no guarantee that'll happen. I would be prepared for sitting separately and if you do get to sit together then consider it a bonus.
Really early is relative. You could eat lunch using the CP package. I think the latest CP seating is an early dinner for most but perfect time for my family, though we wouldn't typically want to attend the latest CP show which is what the dinner CP package seating gets you into.