Was just searching this question and found this thread. I am in almost the exact situation as you were. How did this work out? Did you have to personally check in?
You do not have to check in in person at the resort before using the dining plan. You DO have to be fully checked in, which means you need to get the room assignment text, before credits are available for your use, but even if they're not they will fix it so to me it is not worth the extra time to do that. I have never seen anyone mention this before but this is what happened to us:
Day 1 we went to Tusker House breakfast and the dining plan was not showing. We did a room charge (which was available) at TH and the waitress said it happens all the time, just go to the front desk and they will reverse it and charge it to the dining plan... only I am pretty sure that it got charged back to our Kidani room and then in turn charged to my credit card after our checkout was complete, so it took a little research for them to undo at the BW front desk when we got there (I just left the receipts with them rather than wait around and it worked out fine).
Then we had a 2:30 ADR at Yak and Yeti for "linner". When we sat down and the waiter asked if we had any dining plans I said yes we were on the deluxe but I wasn't sure if it was showing yet. He scanned my band and said it wasn't. An old pro at this I said fine let's just room charge and I'd deal with it at the front desk (I had not yet been to the front desk yet, was at AK all day, lol). So we ordered like we were on the plan and I got the room text while we were eating. Then when it came time to pay the bill he scans my mb again and says "oh good news! your plan is showing up in your account!" So we were able to charge that one to the DxDDP no problems.
It was literally zero hassle to get them to reverse the charge at the front desk (for me, it might have been for them). There was never a line and when it was apparent it would take more than a couple of minutes they just took my receipts and said they would take care of it and I could swing back for the receipts back and that's how it worked. I think it was only more hassle for them because it had already been charged to my card and at a different resort (it was not showing up on the BWV folio at all). At no time did they act like they would not be able to fix it, just that they could not fix it quickly right that second.
So all that said I would not take the time out to check in if it is not in your plans. I'd just go with the flow and then let the front desk at your new resort sort it out. I'm pretty sure because of the sequence of events at Y&Y that once you get your room text you are full checked in (whether you have gone to the resort or not, we haven't) and at that point you should be showing your dining credits on your bands. Hope that helps!