For a 2:48 flight, you will have a pickup time of between 11:30 and 12:15...ish. DME picks up about 3 hrs before flight time, give or take 15 mins either way.
You need to be back at the resort, ready to go, about 15 mins before the stated pickup time. That pickup time is the time the bus is due to leave the resort, not the time you should be arriving to get the bus!!
Have everyone in your group together, bags with you, all ready to go, out at the DME bus stop. I have sat on many buses where one of two things happened with groups with missing family members.
1. the driver sat there and waited until the tardy members showed up, thereby annoying those already on the bus.
or
2. the driver said..oh well...and left. Family members actually got off the bus rather than go without part of their group...they were left at the resort to find other means of transportation back to MCO.