We absolutely love the idea of a birthday time capsule. Not only does it create a sense of inclusion amongst your friends and family (even those who are unable to attend), but it also gives you something to look forward to down the road. Put an enclosure in with your invitations asking every guest to contribute a memory, note, or "sign of the times" for the capsule, then bury or hide it until your child's 18th birthday — or whenever you deem the right time.
Create a Birthday Time Capsule
Source: Hostess With the Mostess