Pudong International Airport T2 to Hangzhou West Lake

My family of 4 plans to head direct from the airport to Hangzhou in one of the weekdays in Dec. We plan to buy the HSR tickets only when we reach the station. Will it be more recommendable to take the HSR from Hongqiao Station or the Shanghai Station? What is the chance of no more HSR tickets available?

How about the trip from Hangzhou back to Shanghai? It will be on a Saturday morning. Need to pre-book?

Thanks.