Obtaining GC for the whole family

[Ramsis]

Howdy fellas, I am on my final steps towards obtaining my citizenship and once i have it i want to apply to get the GC for my Father, Mother, and Sister (19 years old).
They all live abroad and i wanted to make a check list with all needed documents that i will need from them so i can start on that asap. I will submit their forms and all needed documents from here in the US and i will put my address down as the mailing address.
They all currently have tourist visa and they can reenter if they want. so my questions are:

1- Is it easier if they get everything done their at the American embassy of the country they are in? or should i have them fly over here for their interview & such?

2- How much am i looking at per individual when it comes to forms and filing fees? I could not figure it out since i could not find for sure how many and which forms i am looking to buy and submit for each one of them.

3- If there is a link for a good thread with details or info for my subject it would be greatly appreciated. The sticky that is up there now is outdated i think.

Thank you