Speaking fluent English gives you better opportunity in foreign companies = better treatments. My cousin manages a team in India from HK. Something you can't do if all you don't speak English. Also HK's main competitor is Singapore where English is the official language.
Even if you go back to mainland China, you can only graduate with 1 foreign language exam of your choice (English/French/Russian/Japanese).
I think all parents put kids into extracurricular activities, not just Hongers. Some may be hockey. Chinese school is just so they understand their old language but all languages are hard if you are not actively using it. As for math class, given there is a huge gap between high school and university math, it's not a bad idea to get ahead of the curve.
Once you have kids, you really don't spend on yourself any more. Priority changes.
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Visit is fine. You just pay for whatever space you can afford during the visit.
Living on the other hand.... this is what $500K CAD buys you.