The downside of the idea here is that the postcards will presumably be sent from where-ever they are (e.g. some place in the US) and not from where you are (e.g

The downside of the idea here is that the postcards will presumably be sent from where-ever they are (e.g. some place in the US) and not from where you are (e.g. some place in Italy) so no stamp, postmarks, etc. as well as no handwritten note. Perhaps on the plus side: a photograph you took vs. a professionally shot postcard.