Could not find an ordinance making airsoft guns illegal/restricted in the District, but did find this:
......some municipalities and states place restrictions on Airsoft guns. New York City, Washington, D.C., Chicago, San Francisco, and parts of Michigan outlaw Airsoft guns entirely.
Even if the above information is incorrect, I would bet that you would attract unwanted special attention that might result in considerable expense of time and money.
As noble as I think your intentions are, I don't advise it.