I did online checkin for all 3 of our DVC reservations through disneyworld.com.
Each one showed specific choices for the specific resort, like Carousel section for SSR, or Sunset Savanna for Kidani, as well as "close to lobby", and "ground floor", etc. You could choose up to 2. You could also click the box to ignore those requests so you could get into a room early if possible.
When I go back in to my reservations, I see wording that, paraphrased, asks if I want to edit the online checkin I already did.
"Check-in begins at
4:00 PM
Modify Check-In"
That last bit is a link on my page. I just changed my arrival time for Kidani and I could print the confirmation page if I wanted to.
Now...it took me WEEKS to get all of this done, trying at all different times as the website changed look and functionality. It would error out, it would tell me the server was busy, etc.
I've read several times that it WILL error out if you try to use a Disney Visa CC. (which is just so pathetic of Disney)
And it's all very dependent on your timing and luck.
Since we're still 10 days out from our first reservation (not a DVC resort...our checkin for Kidani is still 17 days away, with two more after that), I cannot prove that this has truly been seen by Disney and will work.
But it sure seems like it has worked!