A cow would provide daily chores that need to get done- not chores that you can skip or put off until later- but chores that effect the comfort of an animal and give you food.
As chores go the only major chore that would qualify as being as important as taking care of a cow 2/day is that of cathing Ian- you just got to get out there and do it, and sometimes even pause what you are doing to get it done. If you go somewhere or are too sick you still have to find a way to get it done.
Sharron Astky at Casaubon's book had this to say about chores
"Chores are a dirty word in most houses - those things no one wants to do. The funny thing is that while the amount of time spent on chores expands when you have animals, so does the pleasure of doing them. It probably seems strange to people that I wrote:
On a farm, chores are something else - they are bookends to each day, a formal structure like the forms of a sonnet or musical scales that shape the day. They can be speeded up, slowed down, slightly elided and occasionally contracted out, but for the most part, they are there, implacable, eternal and oddly pleasurable."
In short chores remind you that live and breathe in a world not powered by the internet.
Besides the value of daily, routine chores the cow will provide milk in exchange for grazing grass and eating hay. The milk will be natural, organic, and grass fed. There will probably be so much milk that we will end up making cheeses and yogurt. (more chores)
Then there is the value of cow manure for those wishing natural fertility upon their gardens. yeah- I know another set of chores of mucking out the barn, composting it and then mixing it into the gardens.
Thirdly is the value of bonding with an animal- in a relationship where you both depend on the other for food.
I hope the once the chores are learned that they can be taught to boys, so the boys can learn the value of the daily chores and hard work and gentleness and firmness when managing animals. I would like them to participate in the circle of life and husbandry, maybe if they can learn to handle a cow, they can handle a wife :)