Just wondering if we send in both part 1 and part 2 or just part 1?

I think you send in both parts but DO NOT sign part 2 as you will sign that in front of the consular officer at interview time. then again, I barely remember my name these days.... wisdom, anyone??????
L.

You send both.
Also separate DS 230s Part 1 and 2 for each family member.

am just wondering isnt the ds 156 and ds 230 , the same thing ?, and if not what exactly is ds 230 required for ?

DS 156 is for non immigrant visas. DS 230 is for immigrant visas!
CR-1 is immigrant!

It depends on country. Applicants from some countries require to send both parts whereas applicants from some countries require to send only part I to NVC. You should go to NVC forum, read the guide, and check the department of state link. I am almost sure that applicants from India need to send DS 230 part I only to NVC. Applicants need to take both parts during the interview, but part II must not be signed until the consular officer will ask the applicant to sign part II during the interview.

You should be told in your interview package.
I only had to send in part I and brong Part II with me to the interview to sign it there. definitely do not sign it until you are there!! Different countries are different though, I know some where you had to send Part II along with the rest. India I am not sure of.