Hi I am planning to go to Hongkong with my family (2 adult+ 1 child) for 6D & 5N can anybody guide

Firstly, you do make a good choice for your hotel which is located near Fortress Hill MTR Station. So the transportaion there is very convinient. But in 6 days, you can also go to Macau for a short traveling.
Here is my advice about your traveling itinerary:
Day 1, to have a rest and wonder around the commercial mall
Day 2, Ocean Park, then to Victoria Peak and Madame Tussauds Hong Kong. In the afternoon, you can descent the peak to enjoy the Victoria Bay
Day 3, Ngong Ping 360 of Lantau Island, then to Disneyland
Day 4, Repulse Bay, Causeway Bay, Central
Day 5, you can go to Macau to visit Ruins of St. Paul's & Monte Fort, Matsu Temple and around
Day 6,to take the free shuttle bus of the hotel to Wanchai Exhibition Center, Century Square etc. and to rest for your leaving.

By the way, since you wanna have a 6 D&5 N traveling, the Octopus Card may help you a lot cause it can be used both at HK and Macau.