Dear MC,
I am originally from Vienna where I grew up and went to university but then lived abroad for almost 20 years, the last 8 years in Hong Kong. In September 2015 I moved to Klosterneuburg just outside of Vienna with 4 kids and my husband, he is Canadian and did not speak any German!
So my situation was a bit similar like yours and while I cannot help you with any contacts in Salzburg I want to try give you a little moral support for your new life because it will be a huge change and not easy!
Your children are the same age as my two younger ones were when we moved and they dealt with the change much easier than my two older ones who were 11 and 13 at the time, so fingers crossed, your biggest worry (will the kids be happy, find friends, like the new teachers, etc) will not be too bad!
I found it much harder for myself, especially during the first year. Moving from a huge city like HK or Singapore back to provincial Austria is a challenge, some people were very nice, others typically grumpy, the level of bureaucracy is mind-blowing, I still haven't found a good yoga studio or gym I like but that comes with the much smaller offer in a much smaller city! I miss the level of service, the friendly people, how well organised things were in HK. But then you cannot really tell people what you miss, because they do not understand, they have never lived abroad, they all say 'oh you must be so happy to be back in Austria' and you think 'no, actually I am not'! I also miss my friends, people were way more sociable in HK, the school was better organised, it was very easy to meet people! And then the weather! I really struggled through the first winter, when it is cold and rainy outside you just don't feel like going out and seeing people, I just wanted to have dinner at home and go to bed! I had no energy all winter to call all friends or so, I just wanted to hibernate and wake up again when the sun came out in April!
But then, there is the good stuff: weekend trips that do not require to get on a plane, we did a lot of weekends on farms in different parts of Austria so that my husband and kids see the country, that's really fun, helping milking the cows etc, going for hikes in the mountains, skiing. Also my children do much more normal stuff here, like riding their bikes to afternoon sports, my daughters are both into horseback-riding, much easier to be organised here than in HK, my sons play ice hockey, and after they have seen a lot of Asia we now take them to city breaks in Europe, again super easy, sometimes we fly, sometimes we take an overnight train which the children love. Food is so much cheaper here, especially organics, Spargel season has just started, all so fresh and nice!
So one has to try and see the positive stuff, my husband was a huge support for me though, he is so positive and was super helpful. What also saved my life in the early days was to get away for a weekend with a girlfriend 6 weeks after we had arrived when I was totally exhausted from unpacking boxes, dealing with authorities, translating endless paperwork for my husband, making sure the kids were happy, trips to ikea etc.
So not knowing you I still wish you all the best, knowing how hard it is to move back after such a long time, much harder then moving somewhere new! Good luck! There will always be light at the end of the tunnel!
All the best,
Betty