We are planning a trip to Aluani May 2018. We have a 100 point contract at BWV December use year. We have no trips planned till this trip in 2018. For this trip in 2018 lets say it's 250 points, will I be able to use banked 2016 points? I say no but I'm being told yes by some people.
I find it helps to think about points this way. With a December UY:
Your Dec 2014 UY points are valid for stays from Dec 1, 2014 - Nov 30, 2015
Your Dec 2015 UY points are valid for stays from Dec 1, 2015 - Nov 30, 2016
Your Dec 2016 UY points are valid for stays from Dec 1, 2016 - Nov 30, 2017
Your Dec 2017 UY points are valid for stays from Dec 1, 2017 - Nov 30, 2018
... and so on through the end of your contract.
For your Aulani trip in May 2018, your Dec 2017 UY points are valid for that stay. If you bank your Dec 2016 points into your 2017 UY, they will be valid for stays from Dec 1, 2017 through Nov 30, 2018 so they will also be valid for a stay in May 2018. You could also borrow points from your Dec 2018 UY if you needed more points for your reservation.
We are also possibly purchasing another 100 points at Poly, would I be able to combine those points with my BWV for use at Aluani? I have to transfer the points from one contract to the other to use right?
If you purchase the same UY and title the contract the same way as your existing contract,
DVC will create it as an "add on" to your current membership. For your Aulani trip you could simply combine your BWV and Poly points to book your stay.
If you purchase a different UY or title the contract differently (include an additional owner for example), DVC sets up your contract under a new membership. In that case, you would need to transfer points from one contract to the other to book the Aulani stay, or book part of the reservation under one contract and the rest of the nights as a separate reservation under your other membership and ask MS to link the two reservations together.