question about Chinese visa.

Nihao, my wife is from Brno,I am a chinese. we want to travel to china for 30 days holiday in May and by the way also to visit my mother. we have 2 children, 1 year and 6 years old. We plane on 25th May to fly, just now We found the valid date of my wife's passport is till to 5th september 2011, our question are:
1,can my wife use the passport it's valid is 4 months.
2,Does my wife need any documents from my mother, If just for tourist visa.
3,How much cost the Fee for my wife with 2 children.my son has own passport and another child with mother in same passport.

Thanks for your rush answer.

Mao.