At the moment I'm not so willing to think the grail was so fully aware that it would have indepently started to plot by offering Kiritsugu a reunion with his family. Kiritsugu knew all the time he would lose Iri, and in fact he had already accepted her demise, so there was no wish within him to use the grail to revive her. There could have been a regret but he's a cesspool of the regrets of a sinner, so what's one more? It's not like being a happy husband and a loving father would have changed his past, in fact it would have only made him a massmurderer and nothing more if he hadn't been ready to see the road till the very end.

So, I maintain my view that it was the grail using Iri's repressed wish to live longer with her family to combat Kiritsugu. Iri was fully supporting Kiritsugu's wish, but that doesn't mean she couldn't have had her own.