You sound very happy and excited about having a chance to get to know him. I think that if you just let him see those positive feelings, and you make him feel welcome, and treat him like family, he will start to feel like a part of the family.
Maybe you could plan some activities just for the two of you, so you can have a chance to be alone and talk and get to know each other.
You might even e-mail him and ask if there are any special things he'd like to do, or places he'd like to visit, since it doesn't sound like he's been to Australia before. How long will he visiting with you?
If you could start an e-mail correspondence with him that might help to break the ice a little before the visit. You could just tell him about yourself, the things you like to do, and find out a little more about him. That might help you both to feel more comfortable with each other before he even arrives.
Do you know if he has a Facebook page? That might also be another way you could get to learn a little bit more about him and his interests.