Family holiday to China from SK

I am Irish born, and living in South Korea. My family plan to come to Korea in May/June. I have just reissued my ARC card at the beginning of this month, giving me only 6 months (up until March) to go to China.

How long does the VISA last for, could I get a one in March, and use it a month or two later?

Would there be much difficulty getting it for my parents, living in Ireland.

We'd look to stay in China for about a week if possible... Any information would be really appreciated

Regards,
Darren