Hello there.
Highly recommend Malacca if you love historical buildings.
While for Kuala Lumpur itself, you may drop by to the KLCC (Twin Tower), KL Tower, Batu Caves, Merdeka Square.
For beach, you may visit Kuantan (around 2.5 hours drive frm KL) as there are beaches like Cherating and Teluk Cempedak.
Some local foods that you may try: Nasi Lemak, Teh Tarik, Roti Canai, Rojak, Ais Kacang...
Well, I'm from Kuala Lumpur. Do let me know if you need any help or I can be your tour guide as i'm currently unemployed due to the redundance..sigh...
I'll be at Penang (food paradise) for this weekend
Enjoy your trip 
Sun