You've received great thoughts from so many posters.
I'll echo, "GO" and add two more ideas:
1) Take a picture! Have the photo printed and keep it in a scrapbook along with the announcement letter. When looking through his scrapbook in future years, there can be conversations about how he felt about this award, realizing that his perspective may change over time.
2) Document, document, document. It is often helpful for parents to begin a "resume" for their child, listing activities, awards, volunteerism, etc. This can be referred to in future years when completing applications for schools, jobs, scholarships, etc.
