Peak travel season to Shanghai?Stand by tickets?

Does anyone know when is the peak travel season from KL to Shanghai?And Hong kong to Shanghai?I have the choice of buying stand by tickets from either KL or Hong Kong to Shanghai and I'd like to know if it's better to buy from Malaysian Airlines from and to KL or from Cathay from and to HK.My departure dates are around 6,7,8 June and am coming back around 17,18,19 June.One of my friends told me that flights from HK around these dates might be overbooked because of the Queen's birthday?So am I better off flying from KL?Thanks a lot.