Hello Doug
Welcome to Poms in Oz.
Timescale: Prolly 18 months - 2 years, depending on your skills. Some of the skills assessment bodies are very slow plus it takes more time than you realise as yet to prepare a skills assessment, and most of it is work that only you can do - eg obtaining references. What does each of you do, please?
Baby: Not a problem. If Baby is born before the visa is granted, Baby can be added to your application. If not, it would only take DIAC in London a couple of weeks to arrange a Child Visa for Baby. However if your wife is pregnant and is therefore advised not to have a chest x-ray till after Baby is born, DIAC will put the visa application on "hold" until you are ready to resume the process.
Offences: Not a problem. Please see here:
Character Requirement - Applications & Forms
Best wishes
Gill