London to Berlin with wife and children

Hi All,

First of all, apologies for the rather long post. I hope you can spare few minutes to read my questions.

I am looking for some general suggestions about moving to Berlin with my family (wife and 3 daughters), from people that have a similar family setup and background.

At work, an US headquartered consulting company, I am being asked whether I would like to transfer long term to our new Berlin office next year (2018). Currently I am living in London, and I am finding the  idea of moving to Berlin attractive for various professional and financial reasons.

However, I am not entirely sure whether it's the right place for me and my family from a non-professional side (education for children, fitting in among locals, etc).

I have been reading about housing, cost of living comparisons, schools. And have a general idea of what to expect. All that said, I was hoping to get more anecdotal insights from people similar to us.

To set some context, here some basic information about my family:
We have 3 daughters that are 7, 4 and 2 years old
My wife and I are in our late 30s
We have moved around already few times (in my adult life: Mexico, NYC, London, Sao Paulo, London again).
My wife speaks English, Spanish and Portuguese
I speak the same languages plus German (I lived as a kid near Hamburg for few years)
My eldest 2 daughters speaks English and Spanish (+few German words/sentences)
My wife studied fashion in NYC, and worked for a couple of international retail brands, and for the last couple of years has been looking after the children.
I am a so called data analyst/data scientist.<- think of people that create mathematical models to forecast events.

Here the topics that I would like to cover

Education for children:
Switching schools system- did your children struggle with that (considering new language, altogether different teaching system). Any recommendations to make this as easy as possible on them?

I could consider international/bilingual schools. My thoughts about this sub-topic are:
The British School in Berlin is rather un-affordable for me, specially considering that I have 3 daughters.
The Nelson Mandela school looks good, but they seem to have some weird admission rules, and I am not certain that we check all the boxes.

What about other English/bilingual schools, which ones would you recommend? Should we aim for a regular German state school right away instead of private?<--  I am reluctant to have my eldest daughter (who will be 8 y/o by the time we tentatively move) go through another school system change because she struggled with that when we moved from a prior assignment in Brazil to London 2 years ago.

Housing:
For those that know London well, currently we live in Herne Hill, and we really like this areas (the cost of properties is altogether another story). Ideally I would like to live in an area in Berlin that has a similar set up. Near to the center, very international, young families, not snobby (but not unaffordably expensive like Fulham/Chelsea area). What areas would you recommend? How much should I truly expect to pay in rent for a renovated (or in good conditions) 3 to 4 bedroom property in such an area in Berlin?

Cost of living/Salary
I read that  the cost of living in Berlin is about 30% cheaper than in London. However, the problem is that this is an average comparison. Things change once you try to compare controlling for life style.<-- We learned this the hard way when we moved from London to Sao Paulo some years ago.
Forgetting for one minute how much I could earn based on profession, experience and age, what minimum annual salary would you say one would really need to live reasonably well in the Charlottenburg/Wilmersdorf area or similar, considering a family size of 5?<-- mentioning these areas because of the bilingual schools.<-- For those familiar with London, if it serves as a base line- we live in semi-detached 3brd property (about 85 sqm), in Herne Hill. 5 minutes away from the nearest train station.

Fitting in/Getting around/Bureaucracy
My wife doesn't speak German- so she would be taking lesson, but for a non German speakers, from a non touristy perspective, how difficult is it to get day to day things sorted? I work long hrs, so I would rely on my wife to deal with things like schools, council related things, etc. Would that be a nightmare for her if she doesnt speak German initially.

Job opportunities for my wife
As mentioned, she is an US educated fashion designer. She worked both in the US and in the UK. How difficult would it be for her to find a job in Berlin in that field (apparel) considering that she doesn't speak German, and likely wouldn't speak the language right away.<-- I appreciate that this is a rather difficult question to answer as there are many IFs.

I would really love to hear from people that have made a similar move to Berlin.

Thank you very much!

Jose