I went there with 3 other families (all cousins) from different parts of India, and we met at Genting (and further to Kota Kinabalu). We all have kids 6-8 years old, and had an absolute blast. Nice rides at the indoor/ outdoor amusement parks which completely empty (as we were there on weekdays during off season), great food (Malay food is splendid anywhere), superb (though old) hotel (I don't remember the name, but we had massive rooms with 2 double beds each). Nights were spent consuming vast amounts of duty free tipple (picked up at KUL
airport or as leaving from India) and catching up with cousins. Days were spent on the rides and keeping the kids occupied.
Kota Kinabalu was much better though - just gorgeous and kind of "untouched". Genting looks and feels rather old/ dated.
This was from January 2011, so fairly recent...