Don't expect the first bus to arrive at Beach Club right at 6:30; it might, or it might be 20 minutes later. But it should get you to MK within 20 minutes, which leaves enough time to get the monorail to Poly. And, as stated, do tell the driver where you are going; he or she may be able to make some magic.
If you're waiting for the bus and it's getting too close to 7:00 for comfort, you can always bail out a grab a cab.