I have 2 probably common but tricky situations when it comes to addressing envelopes.
1. My future FIL has always gone by his middle name (he has the same first name as his late father). When addressing his should I put his full first/middle/last name or maybe first initial and full middle/last name?
2. My future MIL goes only by a nickname, and is quick to correct anyone who calls/introduces her otherwise. If I put her legal first name I will probably hear about it years after the wedding but she's also educated and probably knows the whole etiquette thing, and I might hear about that instead if I don't put her legal name. If I had to choose which one I'd rather hear her talk about, it'd probably be the etiquette.
I was planning on using only 1 envelope but now I think I need 2 (especially for them) so I can feel good about properly address the outer envelopes but they can keep the inner one without the postage and "wrong" names.