Give friends and family self-addressed envelopes with one balloon in each. (For a 28th bday, give out 28 envelopes.) Have them blow up the balloon (without tying it) and write a birthday message on it, then deflate it, put it in the already-addressed envelope and mail it. Your birthday boy/girl will receive the mail and have to blow up each balloon to read the messages.
CUSTOMIZE your own tree with initials- BLUE color version