If you need the money on an ongoing basis then I would change the tax credits etc straight away. Alternatively you can wait and get a nice lump sum in about 12 months time.
Depends on your own individual needs I suppose.
You can get an additional €9,000 of your salary taxed at the lower 20% rate
You can get your wife's personal tax credits transferred to you on a Month 1 basis
You may be entitled to an extra €900 home carers credit depending on your wife's salary for the YTD
All-in-all it could be worth up to €420 per month extra take-home pay this year