And Tango makes Three, Justin Richardson and Peter Parnell
Relevance to Ireland
It happens in the New York Zoo, but nothing should stop you to tell the stroy with the Dublin Zoo instead.
Relevance to 'pink adoptions'
100% relevant, as it explains adoption and gayness in a very age-appropriate manner.
Accessibility
Easy to read, and very engaging, especially when the egg cracks open.
Rigor
One item may confuse the child: Tango's egg is nurtured by her two fathers, and they are in effect her birth parents (but she is not their biological child).

Overall
It s a loveable story, and very good to approach the topic of sexuality at a later age. The sad part of the story is that the couple did eventually split...

When she reached breeding age, Tango paired with another female penguin called Tanuzi. As of 2005, the two had paired for two mating seasons.
In 2005, Roy and Silo separated, after some six years of paired behavior, with Roy remaining single. Silo found another partner, a female called Scrappy.
As of 2010, Roy and Silo still interact on exhibit but do not display paired behavior.
(Source: http://en.wikipedia.org/wiki/Roy_and_Silo)