Myself and an adult group of 7 people stayed at family castaway and it was great. The place is very spacious and was spotless upon arrival. Davinia is very responsive if we had any questions and we often referred to her local recommendations.
The best part is the large entertainment with and open plan lounge - kitchen - dining area. The was definitely the heartbeat of the house where many laughs and good times were had. We also loved the pool table and made great use of this.
The only negative and a very small one is the house is on the main road that runs through Busselton. There's quite a bit of space between the road and the actual house and shades are provided. It didn't bother us that much but if you're a particularly private person this could be a drawback.
Other than that we had a great time and I would recommend!