I just want to say enjoy your trip. Pooh's comment pretty much touched on everything I could think of and more (It's called Astrill VPN tho, pay once and both you and your wife can use the same account). Use Trip.com to book trains!

One thing we did in Chengdu was a bicycle tour, it was so fun! Though with a little one it might not be as feasible. Also, we just stumbled upon the largest building in the entire world lmao https://en.m.wikipedia.org/wiki/New_Century_Global_Center

We did our trip with Alipay only but we met an Israeli whose hotel gave them an invite to WeChat. The only shortcoming with Alipay is that it didn't allow us to 'transfer to individuals '. I don't recall know the difference but if I wanted to pay someone they had to have a QR code to scan. So, cash can be useful for cabs or whenever someone doesn't have an Alipay qr code (sometimes they'll only have a WeChat qr). Funny story they only approved the Israeli visa for 30 days, single entry whereas our Canadian ones are valid until our passports expire.

Guilin is beautiful, I trust you will also go to Yangshuo to see the Lijiang? There's a really fun buffet type restaurant called Changji(I think) in Guilin. My hotel recommended it, their signature goose was the best I ever tasted.

I also wish you a very 'get accosted by schoolkids learning English in Hong Kong' 😁 and enjoy the beautiful parks. Oh, and AlipayHK never worked for me .. you can use cash or credit cards

When you return you must give me your tips from Shanghai/Beijing! So excited for you comrade. I wish I could go back already