Be prepared for unexpected cool days and rain - a warm jacket, a sweater, and an umbrella should cover every weather contingency. Don't leave your baggage unattended. Never accept mystery packages from strangers. So can each member of your family, regardless of age, and your exemptions may be pooled, so one of you can bring in more if another brings in less. Larger stores will handle mailing for you.
Sockets are the two-pin type.
Don't bother with voltage converters - they have never functioned satisfactorily for us. If you can find battery-powered appliances, make sure they run on AA batteries which are readily available in Germany and Austria. These numbers do not require coins at pay phones. There's usually one, all-night pharmacy in each town. Pharmacies post a list on the door, telling whose turn it is to be on call.