All that matters is that you DO have a reservation. And as many have said before me, the fact that you received your personalized, pre-printed DME luggage tags is proof that you have a reservation. Disney doesn't print these up for all guests, they are printed ONLY for guests who have DME reservations.
Also, as noted above, they really don't care about your flight number or arrival time. They gather that info so that they have a pretty good idea of how many people will need a bus (and luggage delivery) to which resorts at around which times. But it's not like they're sitting there waiting for you specifically, or if you showed up early or late that you would not be accommodated.
All bags with DME tags get pulled from the usual luggage stream. They get scanned several times during their journey. Meanwhile, you will check in at the DME Welcome Center. The computer will reconcile the fact that you checked in, AND that you have luggage in the system. Everything will be great from that point on. At the Welcome Center, they'll even ask you how many suitcases you checked and tagged, so they make sure they have all of your bags and not just some of them.
Hopefully, all of the info in this thread will assure you that you truly have nothing to worry about.
Have a magical trip!