How does slaughtering a cow or a goat etc. show their willingness to sacrifice own sons and daughters for God?

Across the World, Muslims are celebrating Eid where they sacrifice millions of goats, cows etc. to commemorate Abraham's willingness to sacrifice his son for God. Why can't they give their own head instead of their son or sheep or cow? Now, some of you would argue that I am being disrespectful to another person's belief, but logically it makes no sense to me. I have no problem someone sacrificing or devoting one's life for betterment of overall humanity and standing up for peace, justice, equality, freedom and righteousness and God. Our own Sikh history is full of great stories of human devotion to God and Guru that goes beyond caste, creed, gender, religion, race etc. The five beloved ones (Panj Piyaray) didn't offer their sons or daughters but themselves to Guru Ji for the sake of panth. Guru Arjan sang songs of God while sitting on a hot burning plat. They could have easily send their sons or daughters or wives to devote lives to God than themselves. Sometimes, I even have problem, when people say, oh! Guru gobind Singh Ji sacrificed his father, mother, sons for the panth. I can accept that with older Sahibzadas since, at 14 or above age, a person can make a good decision for him or herself to fight in a battle, but the younger sahibzadas were both under 9. Guru Ji had no choice for the younger sahibzadas, since he was physically separated from his mother and younger sahibzadas. I have no doubt that he would have done everything in his hands before allowing his sons to be bricked alive. Another question comes to mind, when does the choice becomes personal and when is it a parent responsibilty? Being a father of three myself, the question always comes, what would I do if situation like that comes. It is no easy task yet people make it seem so easy. It is just like sending your kid to army or navy or air force. Would I tell my kids to not join army or airforce or navy? Anyways, without going off on tangent further, I don't understand the significance of slaughtering of millions of cows, sheep and goat for a mere ritual. I would think God would want a personal sacrifice for humnaity than a mere head of a goat or sheep or a cow to show your love for God. I appoligize if the writing is offensive, but the intent is understand why things are done certain way? Afterall, Guru Nanak sahib taught us to question rituals and keep things practical.

Anyways, to brighten things from this sad topic, wish everyone a happy, healthy, peaceful and prosperous 2007! May Waheguru bless all the creatures of this Earth and bring peace! Nanak nam chardi kala, tere bhane sarbat da bhalla!
http://photos.reuters.com/pictures/slideshowrefresh.aspx?id=0&name=633028736352500000&dat=28%20Dec%202006&title=Eid-al-Adha+Festival+Around+The+World&src=122806_1101_ARTICLE_PROMO_also_on_reuters