wife will simply come on visitor visa for time being
She might face difficulties in being granted entry (and could be refused entry) as a visitor if you and your son are British and you are living and working here (settled). It could be seen as trying to get around the immigration rules for spouses. My honest advise would be to apply for the proper visa before she travels.
She cannot switch to any other visa category from within the UK as a visitor and will have to leave the UK and return to Australia to apply for any further visas.
Spouse visa (based on your British citizenship) Spouse Visa (Click)
* You need to earn a minimum of £18,600 per annum and have 6 months worth of proof to show this (payslips, banks statements, employer contract and letter etc.
* Or you need to have substantial savings of £62,500 held for at least 6 months in an accessible account.
* Proof of sufficient accommodation
* A spouse visa requires 5 years residence (2 x 2.5 year visas) before she will qualify for indefinite leave to remain and subsequently British Citizenship.
* Pay £956 for the visa application fee for the initial 33 month visa/entry clearance.
* She will need to apply for a further extension on FLR(M) for a further 2.5 years, paying the visa fee and meeting the income requirements as above.
* She is free to work for any employer.
UK Ancestry Visa UK Ancestry Visa (Click)
* This visa only costs £324 and is a single visa valid for 5 years (no extensions and additional fees needed) and she will qualify for indefinite leave to remain and subsequently British Citizenship 5 years.
* She will have to prove her ancestry, documents easy to obtain in the UK if she doesn't have them, i.e. relevant grandparent birth and marriage certificates, relevant parents' birth and marriage certificates, her birth certificate. All need to be the long/unabridged version.
* Proof of intent to look for work.
* Proof of accommodation
* Proof (bank statements) to show that she has sufficient funds to support herself for up to 3 months.