It has been ranked the most liveable city in the world for some years in a row.
Cost of living is low compared to the European average; you can rent a medium-sized apartment for 600-700€/month.
Everyone speaks English. Co-workers from Spain never bothered with German, because they can get anything done in English.
Viennas public transport system is cheap (30€/month) and excellent. You can get anywhere in the city in a reasonable amount of time. Generally, all public infrastructure is in great shape.
The tech-scene is so-so. It's certainly not London or Berlin, but there are some startups if that's your thing. There are plenty of enterprise IT jobs in banking, insurance or government.
Education and healthcare are free and nature is close. It's a 1 1/2 hour drive and you're skiing in the Alps; 2 hours and you're in the Salzkammergut swimming in mountain lakes.
All in all, it's a great city to raise a family.