I visited a few years back and did KL, Penang (George Town) and Langkawi
KL is a big crazy city, a few nights is all you need though. Lots of good food and great cheap street food. The street food in KL is amazing and cheap (Chinese / Indian / Nonya).Interesting things to see like the night markets, just to sit round and people watch. Would definitely recommend a food tour, we did this one –
https://www.tripadvisor.co.uk/Attraction_Review-g298570-d1955672-Reviews-Food_Tour_Malaysia-Kuala_Lumpur_Wilayah_Persekutuan.html
George Town – is Penang’s capital city. It’s a really interesting place to wonder round, it’s like it’s been frozen in time. Amazing street art and cool buildings hid down every little street. Street food again is some of the best I’ve had anywhere in Asia. Just google it! My favourite place we visited in Malaysia.
Langkawi – Beautiful tropical island, still easy enough to avoid the busiest bits. Best thing is to get on a boat for the day and discover what the place has to offer.