The man in the cart could be John, he had taken the reins before in her life and led her on a safe journey--their life together with their children.  She recognized "him by his hands, driving the cart."  She did not have to "look in his face" because she knew him without seeing.  He drives her down the tree laden path among the thousand birds that "were singing a Mass.  As John had protected her in her life, he comes to her at the time of her death to lead her to a safe journey to heaven.

I've always found this symbolic of her journey into the afterlife.  She is stepping into the carriage/cart as she begins to die.  She recognizes the hands, it says, and this could reference God or Jesus...quite frequently, I've seen images of the hands of Jesus or God depicted in paintings, church stained glass windows, etc.  Perhaps it was John or George or both men in spirit, who have already taken this journey and who are there to travel with her.  I can only speculate. :-)