When you say make a reservation for Thursday, you are meaning that you would basically "throw away" the points for the Thursday night just to be able to check in early on Friday...is that right ? That seems like a pretty high price to pay for checking in early.
As far as will the resort cancel your reservation, I would say no cause you are still using your points for Thursday night so how could the resort cancel you out. This is not like a normal hotel where if you don't show up the hotel will cancel you and rent to someone else. Plus if you do not show up on Thursday night, the room should be ready and waiting for your at 8am on Friday...just like it was ready and waiting for you on Thursday night...you paid for it so it should be ready whenever regardless.