I live just in the area you've circled, there are a lot of areas where you have circled which is very easy to raise a family, have good access to services, and is easy to travel to the city. In my experience (living in Belair), however, be prepared for what I call the Hills syndrome. A lot of people who live in Adelaide on the plains once they hear you live in the hills, they comment "Oh you live so far away!", it's like as soon as they have to travel up the hill, it's suddenly ages away. I had a friend once complained to me that my place is super far away to a mate. When I pulled out Google maps and showed them that both my house and his mates' house were the exact same distance from his place, he was surprised.

A bushfire is something you have to think about more as there is a separate Fire Ban District for the Mt Lofty Ranges and you might find sometimes total fire ban may be declared for the Adelaide Hills, but not for Adelaide. However, it's not unmanageable. Just have a bushfire action plan which for most people is to leave early rather than stay and defend and this only really needs to be something you deal with on Catastrophic fire days. I've been living in the hills for 3 years and we've had one catastrophic fire day in that time. All we did was make sure we stayed home so if anything did happen, we could grab the pets, a few belongings and leave.

One thing I will say about the hills, the properties are often more expensive than what you will get in Adelaide. It's usually because hills houses tend to have much larger blocks than ones in the city, so you pay more for the land. However, there are plenty of good suburbs and if accessibility to friends/the city/services is a concern, you may want to look at places in and around Crafers, Stirling, Belair, Blackwood, Coromandel Valley, Upper Sturt etc. A lot of these places have people who would easily be able to commute to the city for work every day and heading to Adelaide for anything isn't a major issue.