Unfortunately not. Dining plan credits are not transferrable. They may only be used by the person who purchased them.
All the literature for the Dining Plan explicitly states:
You may not use your Key to the World card to redeem meals or snacks for Guests who are not on your Disney Dining Plan.
You can find this, and other information about the Dining Plan on the Disney Dining Plan brochure. The brochure can be downloaded from the WDW website.
This includes a listing of all restaurants that are on the Dining Plan,
as well as additional information about number of credits used, counter
service vs. table service, etc.
To download the brochure, click
HERE, then click on the Disney Dining Plan card, then click on "Download Disney Dining Plan PDF."