Just come across this thread & the answers really made me laugh.
My bestist friend always writes either a random 'price', or a little message like 'nosy', on the back of my birthdays cards - so I do it to her now!
Seriously mrs.chappie, p'raps you could buy some stickers from a stationers to put over the words & year? Mind you, some nosy person, migt peel it off to investigate, lol.
You must be a bit concerned about sending them otherwise you wouldn't be asking us & to be honest, I'd be exactly the same. I think to save face, I'd probably end up recycling them & starting again, although we're all different. ;o}