I may be a bit late if you've already decided but I lived in Shanghai for 18 months and left 6 months ago. We enjoyed living there - here's a few of my feelings about the city:
It's very urban and we really missed green spaces and a bit of wildness. There are parks but they can sometimes be quite sterile, 'keep off grass' and 'no flying kites' signs etc. But there is a lot of travelling you can do through China to see some incredible places, so it kind of balances out. And the city itself has some really interesting architecture and districts like the very new in Lujiazui (Pudong) to the old French Concession and the Bund (Puxi).
Shanghai is considered expensive but cost of living is low compared to the London (which is where we move from) and the food there is amazing - the range of Chinese food is great but there are also loads of international cuisine options. We really loved it as a foodie city as there is so much choice and eating out is so much cheaper than the UK.
The weather is not lovely. Not just the air quality, but summer is very hot and humid, 40+ degrees and May/June can be very rainy. Winter is very cold and most flats don't have central heating, but will have an air con unit that can do heat as well. Spring and Autumn are lovely but last a matter of weeks each.
The mobile landscape is incredible - almost everything can be done via app. Often we would leave the house with only keys and phone and that would be it. Some apps are only in Chinese though, so it's good to have a native speaker friend who can help you navigate through them the first time. I've left Shanghai and moved to HK now, and it's like stepping back in time in terms of how un-mobile friendly everything is.
Language - Shanghai is generally fine for non-Chinese speakers, all road signs, metro signs, shopping malls, international restaurants etc will have English language materials as well as Chinese. Taxi drivers can be hit and miss, you would generally need to know the address of where you are going in Chinese, not many speak English. I would really recommend getting some lessons though, my boyfriend took a couple of months worth and found it made life infinitely easier in taxis/shops/restaurants.
Censorship - this was probably one of the most annoying things. Even with a VPN to get around the Great Firewall, the internet was slow and patchy. Daily frustration trying to google stuff for work and having to use Bing or Yahoo. Having to ask friends and family back home to download WeChat because it was just such a faff to get WhatsApp to work. Really annoying but not a dealbreaker I guess.
I notice you said your DH doesn't speak Mandarin - in the end, we left Shanghai because my boyfriend just struggled too much at work. He worked for an international company (transferred from the London office) but within weeks was hitting roadblocks and basically couldn't do his job without the language. It was unexpected, as the company had led us to believe this was a great opportunity for him and that language skills wouldn't be an issue. My boyfriend does recruitment which is very different from Engineering though so it may be a completely different kettle of fish.
I think it would be an amazing opportunity for your kids. Despite the negative aspects of the pollution, censorship, government, human rights etc, China is very cool country to live in, there is so much to see and do, and the people you meet are generally friendly and helpful.
Good luck with your decision!