I asked at check in because we had planned to be at
MNSSHP at WDW that week and had to make a last minute change to DLR. She said to come to the front desk at 5am the day-of. I went down at 4:45am and was the third family in line. They took my room keys, park tickets and credit card. They had a hand written list in order. At 5am on the dot, the CM started typing on a computer and calling up families in the order that we signed up. They printed the tickets out for OBB right there. They said there were a "very small" number of tickets which were shared by all 3 onsite hotels, and it was first come, first served. So hope your CM has quick fingers. There were about 15 families in the line, and they announced that all would likely not get tickets that morning. I did not stick around after we got ours, as I hopped back in bed!! I had called DL and the hotel several times in the 1-2 weeks leading up to the trip to try to confirm if same day tickets might be possible, and no one would give me a definitive answer until we actually checked in and asked that CM. So it is risky to count on it, but we were going either way, so it was a bonus that we got the tickets!