Thank you. Some further questions.

Both parents are principal applicants correct?
Evidences to provide:
Copy of receipt of I-797
Two photographs each (as specified)
Copy of passport page as ID
Birth certificate
I-94 record
Passport page with B2 visa
Marriage certificate (may not be needed if both parents are principal applicants)
I-864
Evidence of financial support(affidavit)
1140 bucks. Cashier check or regular personal check is fine?
I-693 at a later time