Doing my first wedding next month, help with matching lenses between an a7s II and a t3i?

I'm trying to figure out what lens combination I want to use for the vows, and also capturing the rest of the ceremony but the vows are my main concern that these be perfect, because for the rest of it I think I can just film with my a7s II. So I need a lens / setup combination that will match, I'm going to be renting lenses and my local shop has pretty good selection, can anyone suggest a way to make the footage from the two cameras match? I haven't even gotten the a7s II yet, but I've heard you can put it into cropped sensor mode, so I was thinking if I did that that could help. Thanks very much in advance