There is also the option of heading to Phuket. The flight from KUL is just over an hour, and there is an international airport on the island. Malaysian has a flight leaving KUL at 6:10 pm (meaning you could conceivably leave after a day of meetings) arriving HKT (Phuket) at 6:25 pm. You'd be ready for an early morning dive. Assuming two days of diving, you could leave Phuket on the evening of the third day (after your no-fly time) on the 7:20 pm flight and be back in KL after three days and three nights away.
Unfortunately, you will be in the region exactly at the change in the monsoon, so there's a pretty good chance you'll get rain regardless of which side of the peninsula you decide to go to (S. China Sea side for Tioman/Redang or Andaman Sea for Phuket).
If you want more Phuket info, feel free to PM me.