Have every family rent their own points.
DVC rental transactions are often final (through brokers, through individuals you should consider them final - some members will try and work with you, but it isn't always possible). With a big group, life can get in the way - and you don't want to be out money (I wouldn't rent DVC points at all for this, because someone is going to need to cancel and end up with hard feelings being out money).
Fifteen years ago or so I started to plan a family trip using my own points for my own family. With my own points, I gained some flexibility over a rental. I planned it almost two years out to get buy in. Well, my sister got pregnant and was either going to be huge or have a tiny newborn - and asked me to move it. I did, I moved it a year. Well, after the baby was born, she found a lump in her breast. And we pushed it again, giving her a full year for chemo, and another for recovery - Disney with her two boys while still low energy from chemo was not a great idea. During this drama, my baby sister broke up with her long term boyfriend, entered rehab twice, and by the time we traveled, had been unemployed due to her alcoholism and was only a few months sober. So a trip that started with my parents; my husband and I and our two children; my sister, her husband and one child; and my other sister and her fiance happened five years later with my parents; my husband and I and our two children; my sister her husband and her TWO children. My other sister decided to stay home. (Everyone is fine, my sisters are both good - that was the final trip through rehab for the youngest and the other one has a set of perky new breasts).
Once in a lifetime problem? Nope. Years later my husband's brother got cancer and we scheduled a cancer recovery trip for him when he got his clear. The trip was to be us; my in laws, and my brother in law and his girlfriend. The cancer came back and he passed away, and my husband and kids and I spent four days in a Grand Villa by ourselves.
Pregnancy and cancer are pretty dramatic, but people also loose jobs and have to reassess the spending, marriages fail. Or they just decide that the priorities don't align - their kid is really good and soccer and has a major tournament that weekend. Big groups need flexibility a DVC rental doesn't give you.