The letter idea is absolutely adorable, and if you want help with a cute poem, I gotchu bae.
I think if you are running out of time, you should totally confess. If you are good friends anyway, you can still hang out until they are gone.
Idk what kind of bracelets you are talking about but friendship jewelry is an awesome idea!! Hot topic has a bunch of cute friendship chokers, necklaces, bracelets, etc.
Love you!