Hello Roddy
Wlecome to Poms in Oz.
Let is start from the bottom of this pyramid and work our way up through it, I suggest.
26 year old son: He is now too old to be classed as being dependent on you, so in order to migrate he would need a skilled visa in his own right. Whether that is possible depends on what his skills are, what his experience in the relevant field is and (for the moment but not necessarily indefinitely) whether or not he has qualifications in the relevant field that the relevant skills-assessment body in Oz would be prepared to accept.
25 year old daighter & her Partner: As above.
22 year old daughter: She might still be dependent on you if she is still in full-ime education and has been since leaving school. If not, then the chances are that she would have to do the same as her brother and sister.
You & your wife: How old are you, please? If you are under 55 you might just about be able to get an Employer nominated skilled visa, but you would have to be able to satisfy the age-exemption criteria, which are here:
Regional Sponsored Migration Scheme (Subclass 119/857)
The closer you are to 55, the harder this would be to do. Also, you would need a skill in the relevant groups of the MODL. Please see the following links:
Is your occupation in demand? - Workers - Visas & Immigration
A-Z Occupations List - Australian Skills Recognition Information
Employer Sponsored Workers - Workers - Visas & Immigration
Information Booklets - Applications & Forms - Visas & Immigration
If you cannot satisfy the age exemption criteria (and/or can't find an employer willing to sponsor you for a visa) there is some sort of Investor visa that you can get if you run your own business, have plenty of dosh and can satisfy the criteria for the visa. To be honest, I haven't a clue about it but I am 51 and if I win the lottery, this option might become possible for me. (So, first win the lottery and then worry about this visa, I reckon, hence I haven't tried to investigate this one!)
If you are 55 or over and can afford an Investor Retirement visa, then that would hold the fort for yourself and your wife but would be of no use to or for any of your children. Please see here:
Investor Retirement (Subclass 405)
This is the visa that Ali's friends the Picketts are on.
In the longer term, if 2 out of your 3 children are able to obtain Permanent Residence in Australia but you can't, then you and your wife would become eligible for Parent migration and could get into Oz that way. Please see here:
Family - Visas & Immigration
Ignore any visa that does not have the word "Contributory" in the title. The Contributory one (if you could apply today) would cost in the region of about £38,000 for yourself and your wife but you would get about £5000 of that back after 10 years.
The non contributory Parent visas take about 15 years (I do not exaggerate one whit) so you don't want that, plainly.
Your easiest and most sensible option at this stage - by miles - would be to have a chat with a reputable firm of Registered Migration Agents. In your shoes, I would ring up both of Go Matilda in Southampton and also Ian Harrop & Associates near Oxford. Both firms would be happy to chat with you for 15 minutes or so for free and with no obligation on your part to go any further with them. I would start by ding that with both firms. The contact details are here:
Go Matilda - Your Gateway to Australia - Contact and Feedback
Registered Australian Migration Agents, UK - Ian Harrop and Associates
If you decide to ring the Harrop Team, use the Burford number and ask for Ian Harrop
pr Tony Coates, I suggest.
With so many different people to sort out, a free 15 minutes almost certainly wouldn't be enough in the long run (but in that event you can always get an hour with Ian Harrop on the phone for not too much money, to try to threash out viable game plans for each of the parties involved.)
In the short term, though, 15 free minutes should be enough to sort the sheep from the goats in the first instance in terms of what is possible for whom. You really could spend a year wading around in the DIAC website becoming more & more confused when so many people are involved.
An experienced Agent with a wide range of knowledge of all the different visas (whch a LOT of Agents do not have but the firms above do) can cut to the chase straightaway and dismiss every idea that is a non-starter, which would save you from the futile pursuit of several ideas that might well turn out to be non-viable red herrings. (The DIAC website is full of kippers, I can assure you!)
Best wishes
Gill