include your immigration status, where you stay and how many household members you got here, where you work, how much you make yearly, purpose of your parent's visit, where they will be staying, for how long will they stay, include you will be responsible for any immigraion violations they do while staying in US.. I included these things in the application to consular office and thats it.
As per documents, you don't need any, just passport and the letter. I would still have some other documents for back up, just in case. Documents like your parents employer letter including how much they make and for how long they are on the leave from office, bank statement, their marriage certificate, and relationship certificate with you and your siblings.
I hope this helps!