If moeslem can only bear a goat to be sacrificed then it is okay and it can be intentionally cut for the whole their family (wife and children). Else, either they can buy a cow for their family or a cow to be shared with maximum 7 moeslems. It is not only cow or goat but also camel, buffalo, and other animal which is grouped in livestock.
About the practical things, still we find any errors done by the butcher or the people who doing qurbani (we call it sohibul qurban). For example, for the butcher, he sometime uses a short knife to cut the animal which tend to be lifted up during cutting. It is supposed to use a long knife rather than the short one because it is prohibited to lift up the knife during the cutting until all of the arteries in the neck have been cut off. Another error is that butcher kills the animal in front of other animal, this action is prohibited according to one of the hadits. Butcher sometimes forgets to say Bismillah before cutting or gives any torture to the animal which are prohibited.
For sohibul qurban, it is highly recommended not to cut their hair and nail starts from 1 Dzulhijah until the day they cut the animal. Sohibul qurban sometimes do errors like selling the parts of the animal directly and giving the money to poor people. They should be given to the poor people first and then if the poor people decide to sell it, then sohibul qurban can help them to sell and give the money to them (not to be sold directly). Sohibul qurban have the right of the parts of the animal only 1/3 and cannot be more than that. Sohibul qurban should buy a good animals which are not deformed. And the last thing is that sohibul qurban can give the meat to non moeslem also but they give the priority for moeslem first (it’s different with zakah which must be delivered to moeslem only.