So what do you usually do with the angbaos received?

I would usually just deposit the money into my bank account.

And this is also what most Hong Kong children are doing as well.

I came across this article which mentions that a substantial proportion of children in Hong Kong are saving their angbao money, of course they might be forced by their parent's to do so but it is a good thing. 

According to the article, many children in Hong Kong were willing to save their money and that it is the best thing to do.