Had the same issue recently as we are five traveling and one is EBG and one EBS so in total we have 8 bags which is way too much. Ended up booking all as Smart to avoid two bookings though.

In in terms of lounge and fast track it should make no difference. SAS chat told me that there would only be fast track for me (EBG) but at CPH I think I can bring the family.

So main thing to consider is probably advance free seat selection if there is a EBG in just one if the separate bookings.