You wont have trouble bringing in commercially sold snack foods into hong kong such as the ones you mentionned. For nuts i'd bring them in their original package (avoid bringing what is sold in bulk in unmarked ziplocks), just in case you get a disgruntled custom's officer.
As for finding snacks in Hong Kong, you will have no trouble. You will recognize many western brands in 7 Elevens or supermarkets such as Welcome. You might even find your children hooked on Pocky or mochi ice cream.
The only thing i find less of in HK is cheese and dairy products. Not sure you can bring that through customs anyways.
Edited: 5:50 pm, February 21, 2011