My 2c.
I don't necessarliy buy into the argument of 'dead money', you are getting something in return, it might not be yours to keep, but it is something tangible. You don't have to worry about things like broken washing machines, burst pipes and management charges if you are renting. Buying a home gets you much more than just a roof over your head!
BTW, I currently own my own place, I rented for around 8 years, and I don't have any property investments, so have no vested interest in advocating renting vs. buying.
Given the fact that both your daughter and her partner earn less than €92,000, maybe the is a viable option over you actually buying the house? While waiting for approval, they could rent in the meantime (they should be able to get a place for less than €1200 per month if they 'shop around') to see if they want to make it a long term arrangment).
Of course, if you want to go ahead and buy them the house (given all the tax and other implications outlined above) and your daughter and her partner are happy to accept this arrangment, then fair play and all the best.