It may be worth running your case past a registered migration agent - as you may have issues including your eldest child on your visa if he is working, to make sure that you dont have any issues - and can show he is fully dependent on you it would best to get advice. As it can be very hard to get a family member to Austrlalia when not included in the original visa application.
Originally Posted by soccer65
You will need a positive skills assessment and IELTS before you can lodge your EOI. (It is not worth lodging before if you dont meet the requirements as it is only valid for 2 years) 190 visa requires State Sponsorship - most states once you lodge your EOI you can approach the state for sponsorship if approved you will be invited to apply.
Your occupation assessing authority will have a list of people that can certify documents - but a JP or solicitor can.