We don't really know all the intricacies of the algorithm. EK hasn't published the details, and most of the active FT members here either travel in premium cabins or have status when in Y, so we've had relatively few reports from pax. In my experience most pax (seemingly not all, not sure why) are auto-assigned seats shortly before OLCI opens. In appears to be Front-to-back but I have no idea who bookings with multiple pax are handled. Beware that what you perceive as off-peak isn't always off-peak for everyone else and EK can fill planes on surprising dates sometimes. That being said people shuffle around so if you are separated get as many together as possible and keep checking the seat map every hour or two and you'll find seats opening up and closing as others check in and amend their assigned seats, you may be able to get the remaining lone members of your group next to or near the main huddle