Is there a reason you've opted to drive/park at MCO instead of driving to and parking at Port Canaveral? Just curious since if I needed to pay for parking somewhere it would be logical to park at the port and not pay additional for the DCL transfers.
DCL Transfers from MCO do need to select a PAT (Port Arrival Time); transfers from the MCO Hyatt do not. That said, you will be allowed to board the bus and subsequently enter the terminal upon arrival. Your boarding group number is tied to your PAT (earlier PAT = lower boarding group), so your group will likely have different boarding groups. If you want to board together, DCL requests that you wait until the higher number is called. It is likely that "open boarding" will be called sometime between 12:30/1:00pm meaning anyone can board regardless of PAT/boarding group.