Hi,
I'd concur with an 8" inch dob. Collimating is nor here nor there. I'm sure there would be locals in Mackay whom could show you how. The other thing to consider is if no one in the family has an iPhone, ipad or I touch, If so consider purchasing Sky Safari - it's great for understanding the night sky for navigating, not to mention the educational aspect of it.
Good luck
Norm