The Obama-Biden transition team is only accepting mail in #10 envelopes. It is unclear whether this policy will extend to the White House. The current White House statement on packages is: "Items sent to the White House often experience a significant delivery delay and can be irreparably harmed due to the security screening process."
If possible, you may want to consolidate several poems on a page and try to fit it all in a business size envelope or email email@example.com. Or try some of the Dana Gray Elementary students' suggestions below!
You may also want to send copies of your letter and poems to your senators and congressional representatives.