CRT (and the 3 dinner shows) are funky with this.
For starters, you DO need a booked trip with an applicable
DDP in order to avoid the pre-paid portion.
When you book online, there's an option to "use your dining plan" to pay for the meal (or something along those lines). Check that and it'll force you to link your resort reservation with the dining reservation.
Go through the rest of the process and look at the "Amount owed today.." line before you confirm. If it says anything other than $0, you're going to have to call to book it or pay now and be refunded when you dine.
The online system is very finicky and doesn't always catch the dining plans, but if you have a confirmed, booked resort reservation with an applicable dining plan attached, you do NOT need to prepay for these meals.
You WILL still have to leave a CC# though and if you don't show up, or cancel by the cancellation deadline (2 days I think for these), you will be charged FULL PRICE for the missed meals. As a note, if only part of your party shows up, you still MAY be charged full price for those that did not (hit and miss, and under the newest policy they've stated that you don't, but I'll believe that when I see it...)