Sorry, but the Dining Plan is non-transferable. You can "pay" for their meal only in cash, not credits.
The moderators have prohibited discussions about Dining Plan policies, and have asked that if members have any further questions about the Dining Plan policies, that they address them to Disney Dining Directly.
We were definitely able to do this for my Aunt and Uncle in September of this year, and have done it during 2 different trips in 2005 as well. Unless something has changed very recently, we've not had any trouble at all doing this.