I am J1 scholar who entered US in 2006.
My husband is with J2 visa who entered US in 2006.
My son is with J2 who entered US in 2007.

All of us stayed in US for the whole year of 2008.
My husband and I will file jointly using form 1040.

My question is whether I can make first year choice on behalf of my son to be treated as resident for the entire year of 2008, so that I can claim him as dependent and get the child tax credit. Do you think it is doable?

Yes, if you file joint return as residents, you can claim your son. Attach W7 (ITIN applications) with your tax return. Read about J1 tax filing: Your U.S. Tax Return: The U.S. Visas

Thank you very much for your reply. However, there is one thing that I want to confirm.

My son was born in China. Year 2008 is his second year with his J visa in US. According to the residency rule, he should be non-resident alien. Do I need to file extension form first, and then wait until he become resident (July 2009) to make first year choice and file the tax return. Or is there another way to let him to be treated as resident alien for the entire year of 2008?

I really appreciated for your help.

Children usually are citizens or residents of the country of their parents.
Read Publication 17: Your Individual Income Tax; page 26; Citizen or Resident Test -- Child's Place of Residence.

If the child is NOT a U.S. citizen, which means that, to be claimed as dependent, child must spend at least SOME time in the U.S. in 2008.