Well done for getting through it - appropriately dressed! Hope the pastries went down a 'treat' too (pun intended)
I hadn't heard the phrase either - like you, it was just 'tomb sweeping' in the spring & going to 'bai saan' for 'Ching Ming' sometime around the 'Mid-Autumn' Festival (which is complete baloney btw - it's still 25C & humid over here, lol). Don't forget the Hungry Ghost 'Festival' over the summer too - except that one is where people try to *avoid* death, so the kids stay inside (in fear of kidnapping)?
Anyway, all this to say that I'm in a similar situation to you - having to Google most stuff because I don't know what will be expected as 'common knowledge' at family gatherings & what people will scoff at doing because that's 'old fashioned' now. Argh lol...