I address it to my house, post it, then when it arrives in the mailbox I put it away for safekeeping.
These bundles of letters are meant to be a time capsule of sorts; maybe opened when the girls become mothers themselves, or reach some other milestone. Or if I'm not here in the future, I like to think that the girls will have these letters describing what their lives were like as children.
Every once in a while I enclose toy flyers with a toy they received for Christmas that year, or a news article that will seem funnily out of date down the road.
I have also enclosed other dated momentos like money that's become extinct (our $1.00 and $2.00 bills) and lately I have been enclosing a photograph with the letter so they can have a visual frame of reference as they read about themselves at different ages. In our highly digitized age, I'd like to leave a trail of paper so to speak.
What kind of traditions do you have for your children? I'd love some fresh ideas.