About a week before your interview, upload to the "Unsolicited Evidence" option on your online account any evidence of your marital bona fides that you have obtained since you filed (Joint bank account statements, joint utility bills, joint insurance policies, joint lease agreements, etc.) Focus on the evidence that shows that you two have joined your lives financially. A few photos are good too... with those, focus on pics that show you both with friends/family (public life as a couple), not just selfies. To the interview, bring a Cetrified True Copy (CTC) and a photocopy of all civil documents you submitted with the filing. Also bring IDs, Driver Licenses, husband and step daughter's passports with their entry stamp from when they entered the US. Also bring a hard copy of the evidence you upload prior to the interview in case the officer has trouble accessing it for whatever reason. Your Joint I-864 sponsor does not need to attend the interview. If you are at the interview stage, that means that the I-864 was qualified by USCIS during the NBC stage. The field office generally has nothing to do with the I-864 nor do they want to do anything with it. On this note however, if your joint sponsor has filed their 2025 taxes and has access to their Tax Return Transcript, it would be a good idea for you to bring a copy of that with you. Once approved, the Green Card is the work authorization so if your husband and step-daughter's EADs haven't been approved by the time they get the GC approval, those applications will just be administratively closed. Best of luck!