I am a Wills and Estate Planning Lawyer in Queensland. I'll answer what I can lol :)
Also practice in general property and commercial law as well.
Disclaimer:
You should seek independent legal or other professional advice before acting or relying on any of the content here or on the internet generally.
There are free legal advice clinics set up in Qld. See link below for locations: http://communitylegalqld.org.au
Also, I am only familiar with the Qld Succession Law so most of my answers are general or based on what I know in Qld. If you are question relates to a different state, I highly recommend that you seek independent legal advice from that state as it is likely to differ from Qld.
Feel free to PM me if you have any confidential enquiries.
Wills get challenged all the time. Depending on the size of the estate and the family circumstances, a lot of them end up resolving outside of court.
You can exclude anyone from your Will and state your reasons for doing so. However, there are certain classes of people who have the right to challenge the will and make a claim against the estate (e.g. spouse, children (including adopted children) and people who were financially dependent of the deceased).