In the Video Feed the Birds, Mary Poppins is showing these kids an alternate viewpoint about values from the one that their father had. She explains to the children that there are some things that other people do not see. Like the woman who makes a living selling crumbs for people to feed the birds at the Cathedral of Saint Paul. She explains that even people who are good and that we love (the children's father) do not see things, and that it is not because that they are bad, but just unable to see.

In the movie the father works for a bank and represents traditional capitalist values, empire and modernity. Things need to be practical, measurable, and "real"

Whille Mary (The Nanny) is showing the kids that values like caring and imagination are important. 

The father disses Mary values because they do not represent anything real or of substance, like money in the bank. However the next day the kids go to the bank with their father and see the women selling bird feed in the video Feed the Birds. 

In the video Federal Fiduciary bank, the boy decides he wants to give her some money to buy crumbs to feed the birds, instead of investing in the bank. In the Video, Bank Stability, an argument pursues between the boy and the bank chairmen, which causes people to believe the bank is in trouble and causes a rush on the bank. Threatening it's ability to stay afloat.

Demonstrating that the capitalist (money is real)system is no more real then Mary's values, and only exists because of peoples belief and support of it. 

However Mary does not diss  the fathers values, she is just pointing out that it is an incomplete view of the world. Imagination, fun, relationships, love, social justice and religion must also be included in one's world view. The film also points that not only is the fathers viewpoint is incomplete, but that it ignores the fact that the system that he believes in, only can exist because of imagination, right relationships, and values that include trust and honesty.

A similar argument is put forward by Catholic Theologian Dan Finn, in his book The Moral Ecology of Markets, Assessing Claims about Markets and Justice.