Halls Head is lovely. A really nice beach and a good selection of shops and things.
We lived a couple of suburbs down at Dawesville, both of which are part of mandurha. Which is a lovely small city and very pretty with everything you need. My advice is to get a short term rental for arrival and visit each area looking at properties as each area has a different feel. Before we moved, we had looked at a number of suburbs that we thought would be perfect for us, but when we went to look, the ones we thought were perfect were the ones we liked least and ended up in one we hadn't heard of.
Do you have visas yet. What sort of jobs are you going to be doing as mandurha is a commute to Perth.