Salamun Alaikum,
With regards the need to sacrifice, I humbly find from the Quran it compulsory only for those who complete Hajj. Outside that (Those who celebrate Eid ul-Adha etc) it would be charity. However, I personally would strongly recommend charity as it has numerous benefits as well as atoning for one's sins. However, charity does not always mean that one needs to slaughter animals. Charity can be done in many different ways.
I hope that helps, God willing,
Joseph.