BBB in DTD early ADR??
Bibbidi Bobbidi Boutique in Downtown Disney early Advance Dining Reservation?? I hope they don't expect to dine there. 
The problem with relying on WDW Transportation bus service is that buses to DTD run less frequently than buses to parks, especially in the morning.
A DTD bus might come right away, or the group might see two or three buses to each park before there's a DTD bus -- or something in-between. Unfortunately, allowing for a "worst case" would mean allowing more than an hour.
With a "large group," it might take several cabs. That can be costly. Also, there might not be several cabs just sitting and waiting at Art of Animation early in the morning.
I would probably rely on a bus, but would try to get to Earl of Sandwich in Downtown Disney for breakfast before the appointment. (I think Earl of Sandwich opens at 8:30 a.m., but I would recommend verifying that.) I would be at the AoA bus stop before 8:00 a.m. (maybe 7:50 a.m.). If the bus service works out well, there should be enough time for breakfast. But if there's a long wait for a bus, there's still a cushion of time, and breakfast can wait until after the appointments.