I haven't been there in more than a decade (and wasn't a commie at the time*) so can't give advice, but make sure to check out West Lake while you're in Hangzhou! iirc most of the nearby food on the shore is a tourist trap though, so you might wanna arrange meals a little further away, but again, dunno what it's like now. For vegan food, probably look into places catering toward Buddhists (not necessarily vegan but higher chance of vegan items on the menu and/or the people running the place understanding more specific dietary requests), sometimes hard to check even without a language barrier though.

I'm also tempted to suggest taking a day or two to check out Suzhou (Zhouzhuang is super cool and there are a gazillion gardens; Tiger Hill is also interesting but I'm biased cuz I'm into the related history) but that probably makes the itinerary too cramped.

Oh right, this again is probably outdated info but I'd recommend carrying around packs of toilet tissue/wipes as not all facilities have toilet paper. Similarly, some places will only have squat toilets, so that's also something to maybe plan ahead for if it's a concern for anyone in your family.

• I will mention Lu Xun wrote two famous essays on the collapse of the Leifeng Pagoda (near West Lake); I thought it was kinda ironic visiting the reconstructed pagoda but think my feelings have shifted a bit since. It's the kind of place worth checking out once but maybe not a second time, I think, and there's so much to see and do in the area I might not prioritize it personally.