I'm going to give away my sons cat.
Why do you want to get rid of his cat?
I would really love to get rid of the cat because it is really annoying.
That is your son's pet, the animal that he loves so much. How can you tear apart a relationship like this, especially since it is not yours? Your son will be devastated and he will no longer trust you for a really long time.
What if I let him have the cat and buy a better one.
As long as he keeps his cat, you could get another for yourself. Don't take away your son's cat.