Thank you for all your suggestions. We've talked and I think we can come up with some pretty official records, actually.
So, these are the obvious documents that we'll include:
-marriage certificate
-birth certificates for all three children
-tax returns for the last 7 years
-bank account information (this is substantial, since Swiss people collect bank accounts as if it were a hobby. lol)
In addition we have these options of official government documentation:
-our community registration for each of the three communities we've lived in (Here in Switzerland you must officially register in the community you live in, so this shows we've lived and moved together three times. It provides official proof of cohabitation, I suppose)
-our "Familenbuchlein" or Family Book. Here in Switzerland this is more important than birth certificates. It has all of the information (places of birth, dates of birth) for every member of our family. It's a federal document.
We also have some old e-tickets for the whole family (maybe 2 or trips with all our of names listed together as travelling).
Is this sufficient? Are we still obliged to provide photographic evidence? It sounds strange, but sending personal photographs feels very invasive. I guess living here in Switzerland all these years has made me more Swiss. lol We've very few photographs of our marriage ceremony, since it was rather impromptu and we only had a very small apéro after the civil ceremony. We, of course, have family photos, but since I am a photographer... I am rarely in them and my husband is camera shy to a fault. lol Is this an issue?
In addition our documents are generally in 3 languages (sometimes more). French, German, and Italian. I would assume a French document would be acceptable or no? For the German only community documents, should we have them officially translated or is it okay if we provide the translation?
Thank you again for all your help. I really appreciate it.