I coincidentally happend to email Delta about this last week, below is their reply:

"Mileage from the account of a deceased member may be transferred to the surviving spouse. If there is no surviving spouse, then the mileage may be transferred to the executor of the deceased's estate or to the person designated in a will."

This is one area where Delta is actually ahead of the competition. I know with America West miles can either be transferred to just a spouse or child, and I believe with United the miles are forfeitted (I wonder whether they just erase the miles from their books completely, or maybe donate some/all of them to charity?).

So, definitely make provisions for it in your will. Note that since you can't legally sell FF miles or awards, you are a little constrained by what value you put on them. I think the best you could do would be to pick a charity you could/would donate them to (don't know if could be any, or just the ones DL is affiliated with), and find out for tax purposes what contribution they would list for you if you donated miles.

Jeff
Jeff