Depending on the actual dates, I will be keen to join the ride from KL to Penang. Please consider that during Chinese New Year period the traffic can be very heavy, as folks from urban city (KL) are traveling back to home town for re-union dinners and holidays.
The coastal route that you have chosen is definitely less traffic. You may plan for over-night stop at "kampong stay", a type of local Malay village home stay to experience the local village life-style. You can check this out from the Malaysian Tourism web site.