Mary,
All of the Downtown Disney restaurants have in fact been added to the Disney Dining Plan for 2012. That is the good news. What you are experiencing is a lag in getting all the restaurants up to speed on the program. That is just something that takes some time, unfortunately.
It is a 2 Table Service Credit meal as you suspected, so plan accordingly.
I would go ahead and make a reservation. Even if the person taking it is not up to speed on the updates to the program, a reservation is a reservation. One that is on the Disney Dining Plan is not recorded in any differently than one where you are paying out-of-pocket. When you get there, you should have no problem paying with your dining plan.
Also, if you want to see the most current list of participating restaurants, you can see PDFs of all the plans on the page for the
Disney Dining Plan.
Write me back with more, if I can help!
Have a magical vacation!