Tables in Wonderland (TIW) membership is $75 for annual passholders (13 month membership).
There are no discounts for AP on the dining plan itself. The only thing you'll be able to do is book a room/dining package without tickets, paying full price for the dining plan. You may be able to get a discount on the room portion if they are available.
The dining plan is tied to the resort reservation, not the park tickets, which is why you can't get the dining plan at a non-Disney resort even if you have tickets. You must book a package reservation to get a dining plan (except DVC members). Packages usually include tickets, but Disney's come up with the ticketless package so that annual passholders can get the dining plan without having to buy MORE tickets.