Well, you can't take them with you…. why not make sure that your frequent flyer miles and credit card perks benefit someone who can use them? Forbes Magazine has a nifty article about how to transfer those miles — assuming the airline's program lets you.
To see what you need to do, you and your estate planner need to carefully review the small print in the program's manual and decide what may work best given the rules and your plans for future usage. Depending on what's allowed, you might wish to make lifetime transfers, add people to your account and/or leave them by designation in your Will. Your power of attorney may need to have language which specifically directs transfers if you're incapacitated.
Keep in mind that there is usually a charge to redeem or transfer these benefits, so you'll want to expressly authorize your attorney-in-fact or executor to use your cash for that purpose.