Like any other split group ADR, I’d have everyone show up 10 minutes before the earliest one, check in with CM not via mobile, and ask to be seated as close together as possible. MTFBWY!
We did this but it was only 2 people (2 teenage sons) … it worked fine and they did manage to seat them together. But we we prepared Them for the idea of the chance they may be sitting on their own since we did not book a party of 2.