This is good idea, both Rosana's and Granny's. My suggestion is:
We sure need a moderator/organizer;
her/his tasks are:
1. give all participants a number
2. get all the addresses of the participants ( which they can send it by email or PM)
3. after closing date , he/she randomly pick a number (from the other participants) for each participant and send that picked name and address, again by email or PM.
So everybody know where to send the souvenier, by mail
Tasks of participents:
1. send an email or PM to the moderator to be part of this fun with details of mailing address, so only the moderator knows who is taking part.
2. send the souvenier to the other person choosen for them
3. make a picture+souvenier, make LO, and send to special thread for this !! So Granny can do her slide show !!
Hope you can use this