Ummm 成和道 dai pai dong, I practically grew up eating there.
My mother and one of her nursing graduate class mate ran a nursery at #3成和道 in the early 60's. Is the cafe still there? I remember hurrying my homework so I can get my treat of 菠蘿包 (Pineapple bun) and fresh 蛋撻(egg tarts) out of the oven at 4pm.

Happy Valley is a well respected neighbourhood. If you are looking for fun fun then Wan Chai is your place.

There was a saying that it is named Happy Valley due to the income for the government from RHKJC/HKJC.

For getting the directions to hotel there are many hotels which sound similiar to a HK taxi driver. Taxi drivers will get confused. Get the Chinese name printed out and hand it to the driver is the best. Get HK$ for taxi; there is usually no facilities in the cab to handle non-cash payments due to the cost of the equipment.

My plan is to buy an Octopus card upon arrival (from PVG) at HKG at about 6 PM on a weekday.
I understand that they are available at the Customer Service Centre. Is that located after exiting passport control (ground-side)?
Can you purchase an Octopus card with a credit card?

After going through passport control and collecting your luggage, you will exit into the main area where everyone is waiting for people to arrive. That will be the main hall, and the CS center will be hard to miss. You can purchase the Octopus card with a credit card.

There is a MTR kiosk in the "buffer area" immediately after Custom and Excise inspection but before the public meet and greet. You can get your Octopus card there. You may also want to consider some other tourist products offered by the MTR, e.g., the Airport Express Travel Pass. There is also a Hong Kong Tourism Board kiosk there where you are able to pick up some basic information about Hong Kong.

No, you cannot buy an Octopus card with a credit card. You can pay for an Airport Express ticket or Airport Express Travel Pass with a credit card. Cash only to load additional $$ into the AETP.