thank you cards- last question!

i am sure this has been discussed many times- but i can't find what i need in a search.

i am writing all the thank you cards for the eng party- fiance won't do it i'm sure. so when i am writing a note to his guests- can i still write it as i would my guests? i know that you are supposed to say 'fiance's name and i' instead of 'we'.

also, do i sign both of our names on the bottom or just mine? and do i put 'sincerely' or 'love' or something else?

thanks!