KP, I have lost my interest to post any messages for a while. But as an old friend,
I have the obligation to answer your question. In my memory, I-485 filing fee for adult is $255, child under 14 $160. FP fee for adult is $50, no FP for child. The I-485 and FP fees are combined in one check. So for you it is $305, same for your wife. Please write separated checks for everyone and every applications. Suppose you have 3 members: You, Your wife, Your 8-year kid, and you applied I-485 (for everyone), AP (for every one) and EAD (for you and wife), you need to write 8 checks.
Please double check all the fees. My memory may be wrong.
Good luck.