I’m pretty sure if you need to rebook you will have to cancel your old flights and redeposit the miles. Then rebook.

I have enough miles for 3 of the 4 of us to travel at Christmas time. I haven’t flown delta in a few years because we moved and it’s not the best priced option anymore.

I generally know our Christmas travel dates, but it’s possible they may shift a day one way or the other - I’m coordinating with my siblings.

Is it better to wait or book with the miles and pay a difference in fare if we need to change?

Am I correct I can pay the difference in money? This will deplete all my miles so I can’t pay a difference using miles (unless I buy more miles). Thanks!