We went to WDW and used an RCI trade to get a DVC resort week (Beach Club) last April. We also used DME.
First of all, you can get a reservation number from RCI, but that number is useless for DVC resorts. For that you need a DVC reservation number. But don't try to call right after making your trade. You need at least a couple of week for the RCI trade to show up in DVC. Call the DVC number direct. They will talk to you, they are familiar with RCI trades, they will not bite you! They are very friendly and helpful. Once you call them - give them your name, resort, and dates - they will confirm the reservation and give you a reservation number. You can used that number for all call-in or on-line communication with DVC. They can also set up DME, restaurant reservations, etc.
That being said, there is one exception: on-line advance check-in. For that you need a confirmation number (go figure). Ours was in our DME packet. But you don't need advance check in. The front desk will have everything by your name.
We had a great time. The resort room was terrific. And we're looking forward to our next trade.