The CAT thresholds are here
http://www.revenue.ie/en/tax/cat/thresholds.html
so up to 280k would work for your spouse, assuming no earlier gifts.
However, some unrelated questions arise.
Can you comfortably service the new anticipated level of debt?
Is ur missus an only child?
Could they fund a refurb/extension of ur existing house?
Put yourself in the spouses parent shoes and think about:
Depending on how they are fixed financially otherwise, is this the best strategy for them at their age/stage in life, need to perhaps consider homecare / nursing home, maybe in context of the Fair Deal Scheme.
What will they do with 200k?
Are they ready for 200k in the bank?
Are they both independently wealthy?
What happens if he/she puts it all on No 13 in the 3 o'clock at Haydock, or buys a S class Merc?
Could this impact on their Non Con state pensions
I do a bit of work in this area for folk who are not that well off and my advice is give older folk an income stream as opposed to a lump sum and hold on to the PPR as long as possible due to the SW Non Con state pensions means tests.