You should always be 100% truthful in completing immigration documents and when speaking with US immigration officials. Being caught telling a lie generally has far greater consequences than the original offense.
Based on the fact you and your parents were readmitted following your parents religious mission in Brazil could mean that their sponsor had fulfilled the requirements to preserve their (and your) permanent residency during your family's absence.
An absence of 6 over months does not automatically terminate a green card. It is more complicated than that. The USCIS website has information about requirements for preserving residency during an absence from the US.
I suggest that since you have some concerns, your husband has a reason to have all of your paperwork 100% correct, and you want to have the process as trouble free as possible that you should consult with an attorney. You do not have to engage the attorney to complete the documents. You could meet with the attorney to review your history and determine if any additional documentation should be provided; you then complete the documents yourself and have the attorney review the completed documents for errors and completeness prior to submitting them for processing. This approach would give you peace of mind yet reduce the attorney's costs.

