I am not familiar with prefixes in last names, and yet I'm marrying one of those weirdos who has one. 
As someone who frequently uses an initial for her surname at work, I'm at a loss as to how to do that after the name change--and what gets capitalized.
As far as I understand it, my fiancé's last name of "van Rooyen" usually has a lowercase V, except in certain circumstances which just... continually escape me. What should my new initials/monogram look like, for documentation? Do I just forego my middle initial because the prefix would mess everything up? Usually I'm pretty good with English, but this new name, I can't wrap my head around it.
I need a crash course on proper usage. Anyone able to help me out?