Marriott in Greenbelt offered an Indian chef
Martins Crosswinds in Baltimore was marginally cheaper than the one in Greenbelt
Ramada Inn and Embassy Suites Near Baltimore Airport are also cheaper and either offer outside catering or Halal menu
Call caterers directly and ask them- Ravi, Aabshar, Shaheens or Chutney...they often get commission from the hotels and give you a cheaper deal...
Cristal City DC is least expensive by the airports- Crown Plaza Hotel, Hilton Convention Center/Hotel
BWI airport, UMCP, UMBC and George Mason also have venue space.
There are venues in College Park/Adelphi area, but parking and driving time will be an issue.
Good luck!