They're both very similar in terms of beautiful beaches close by, and well connected to Bunbury.
Dalyellup is a fairly new development, with houses still being built around it. Their schools and shops are fairly modern, and they've built a big retail centre in the last 4-5 years. There's also a Gravity trampoline activity centre which my nephews (11 and love. When I visit there's always groups of kids at the play parks and walking to the beach etc, so it appears pretty safe. You're also on the right side to visit Peppermint Grove Beach and Busselton which are amazing spots.
Australind is a town, as opposed to Dalyellup which is a purpose-built development of houses. If you like boating and fishing you have the estuary. Bunbury golf club is also very popular and located in Australind. Perhaps a little more dated than Dalyellup. The main street is also a busy road, but plenty of houses overlooking the estuary and off the main drag. There are some amazing big houses and blocks of land in Australind.
I can't comment on schools, but I suggest contacting them individually and asking for a prospectus. There's lots of school buses that go through both Dalyellup and Australind.
I hope this helps. I grew up in Bunbury, and the South West is a beautiful place to be. If you love the beachy outdoor lifestyle you're in the right place. Best of luck with your visas.