Need some expert advice.

I am traveling over the holidays (NYC to Caribbean) with my family. 8 people in the reservation and we purchased B-class tickets. I will be Platinum by this point. Will I be upgraded with them on my reservation? I know I can get up to 8 ppl in Economy plus.

If I will not be upgraded, should I separate my reservation to get the auto upgrade? Will they lose the platinum benefits of econ+, free bags and priority boarding if I separate?

Any advice or solutions is well appreciated.