Bringing my mom and lil sis for a 4D3N HK trip this mid-March.

Itinerary as follows:

Day 1
Reach HK Airport 10:25AM and buy Octopus card
Take the bus to Casa Hotel (1min walk to MTR YaumaTei) - Check in from 1200 to 1400
The Peak Central = Peak Tram Madame Tussauds Sky Terrace
H&M at Queen St Central

Night 1
From Central, take Star Ferry to Tsim Sha Tsui
Avenue of stars (What's there, really?)
Granville Rd
Harbour City
Park Lane Shopper's Boulevard
Nathan Road/Canton Road
Kimberly/Cameron/Carnavon/Haiphong, etc. if possible to cover

Day 2
Shenzhen day trip (approx. 1hr trip by MTR)
- Windows of the world
- Dongmen Pedestrian Street
- Louhu (or Lo Wu) Commercial Center
- Early dinner at Indus Kitchen

Night 2
Temple St.. Or where ever? Pls suggest.

Day 3
Ocean Park!!! (probably till around 1800 I guess)

Night 3
Maybe Argyle center/
Mongkok New Town Mall/
Ladies St Tung Choi St
Fan Yuen St

Day 4
Flight back to SG is around 2000.
Gotta be at the airport by 1800? I think?
Will be lodging luggage at Casa Hotel.
So pls suggest shopping/sightseeing places I can go to during that 6 hours plus?
Is there enough time for me to go to Citygate at Tung Chung MTR (40mins trip)?

Thanks in advance!