Well , depending on when you are visiting , weather will be a consideration - floods & such . If now , not east coast - Kelantan / Trengganu , Pulau Tioman or where region Tanjong Jara is If mid year than either coasts in peninsula Malaysia should be fine as is East Malaysia where cities like Kota Kinabalu & Kuching are . The best diving spots anywhere in the world are also here .
Liked The Datai , Langkawi but that was awhile ago & management has since changed .
There are cultural centres like Penang ( I prefer the E & O but many new boutique hotels to choose from too ) or Melaka / Malacca ( Majestic Hotel ) .