Yes, the points will be returned to your account in the same status as they currently are in the reservation, providing that you cancel those nights at least 31 days in advance. You will not be able to modify the reservation online, only a CM at MS can do that so once you find the nights, you will have to call.
If you had to borrow points to book AKV, those points will be returned as borrowed points and expire at the end of the UY your August vacation falls.
So, if you have to borrow more points to do what you want to do, then just be sure you don't borrow more points total, between both reservations, that you can use this UY.
Any current UY points from the cancelled nights, if you are still in your banking window, will then be bankable.