The 1879 Blue Book contains a report entitled "Crown Property (Buildings)", basically a list of HK Government owned buildings, and contains an entry for "N & S Pavilion Bungalows", with the "N & S" presumably meaning "North & South". I can't think of any Government building that this could refer to, apart from the building that later became known as "Government Pavilions" on the Mount Kellett ridge. The same entry states, "Commencement of Occupation - July 1879".
The 1879 PWD Report mentions "Civil Service Bungalows at the Peak" being "reconstructed" in July 1879 at a cost of $940. Can't be certain that the "Civil Service Bungalows" are the same as the "N & S Pavilion Bungalows", but I think they are the best fit. Use of the word "reconstructed", instead of the options "constructed" and "repaired" used in respect of other buildings elsewhere in the report, suggests that the building predated 1879. As such I expected to find it mentioned in earlier editions of the "Crown Property (Buildings)" report, but have been unable to so far. Until this matter is clarified I'll go for 1879 as the construction completion date, but it could well be earlier as explained above.
In 1897 the building was leased by the Peak Club (Gov Notification 241/1898). In 1902 "extensive alterations and repairs" were undertaken as the building was "restored to the purpose for which it was originally erected, namely a Summer Resort for Senior Officers of the Civil Service" (1902 PWD Report, Para.'s 17 & 77).
In 1910/11 the building was demolished and replaced by a brick building, also known as Government Pavilions.