Hello MrsBigD! I am on the Upper Northern Beaches - I am an aussie but my DH is German and I lived in Germany for a couple of years.
I have a DS 4.5 who is starting kindergarten next year at www.glenaeon.nsw.edu.au which is a Steiner/Waldorf school as we wanted the German language from a young age. He has been going to a Steiner pre-school in Willoughby last year and this year which has been fantastic. The German International School is actually relocating to Terrey Hills in Jan 08 - which is 5 mins from us and I am planning to put DS2's name down there for preschool. If you get in touch over the email I can send you all the info they emailed me recently if you are interested - it is all going to be brand new and very small class sizes.
For your DD it would probably be just fine and fairly easy to enrol her at the local public school, which are quite good especially when in good suburbs, which is generally what the North Shore, Northern Beaches suburbs are regarded as, although I wouldn't think the classes would be that small. Check out this website - I think it will be useful for a whole bunch of things, but the magazine generally do an issue a couple of times a year of independant private schools www.sydneyschild.com.au/. There are Montessori schools as well in the area.
The childcare centres are generally starting to fill their books for the new year now. Having said that I have never found any trouble getting a spot. The council ones have long waiting lists but the private ones aren't so bad. In fact there is a brand new one opening at Frenchs Forest www.kindalin.com.au.
There is also a deutsche spielgruppe at North Balgowlah Friday mornings which you might find to be a good support.
I would think that a big factor in deciding where to live would be where your DH's work is. Traffic in Sydney can be a nightmare. For example you might want to stick to the north shore train line, or you might be happy to live in reasonable distance from a major arterial road such as Warringah Road or a suburb where he can jump a ferry across the harbour to the city - now that would be something! To test the commute times you could use www.whereis.com.au and for public transport www.131500.com.au
There is also a deutsche spielgruppe at North Balgowlah Friday mornings which you might find to be a good support.
What kind of work would you be looking for?
I hope that helps some, Sim