We had an odd experience with a similarly timed BoG breakfast. Our ADR was at 8:05. We arrived at the gate at approximately 7:45. There were three parties in the line in front of us, one had some kind of issue and it was taking them forever. Right before the group in front of us checked in the woman checking people in for breakfast announced they would not be doing any additional check in and told us we had to get in the regular park entrance line with everyone else. It's now probably 7:55 and the lines to get in with everyone else were crazy long. I freaked out because that left us with only five minutes to get though the lines and back to BoG. Everyone in the breakfast check in line was shouting their same concerns but she told us we would be fine as she walked away. We got back to BoG about 8:10 or 8:15 and they didn't even blink that we were there late so it really was fine - it was just a stressful way to start out the day. That's the only time we have ever had that happen with an opening time breakfast. We've even been let in early for ADRs that are 15 minutes after opening. Not sure what they deal was that day but based upon that experience we now get to the gate closer to 30 minutes before our ADR just in case.