Your husband can claim the Home Carers tax credit (worth about 1K)
He can also transfer your individual tax credit to him (but not your PAYE credit), and some of your standard-rate allowance (talk to Revenue about this).
re: PRSI - for pension purposes, provided you're receiving child benefit, years spent not working won't affect your entitlement to the contributory pension. Not sure about other PRSI benefits (there aren't many others anyway - unemployment benefit, eh... that's it I think).