Both films are by Isao Takahata. Pom Poko (http://en.wikipedia.org/wiki/Pom_Poko) is like the anime version of a Dr. Seuss book about the dangers of urbanism and environmental destruction. Pom Poko features a tribe of talking raccoon dogs who face the impending destruction of their enviroment, way of life, and community by encroaching suburbanization. I believe this is based on a real fight against the expansion of Tokyo in the 1960s.
Only Yesterday (Omoide Poro Poro, http://en.wikipedia.org/wiki/Only_Yesterday) is a 1991 anime film by Takahata about a young woman living in Tokyo who goes on a trip to visit relatives in the countryside. This movie has lots of adult themes, so it may be more approriate for young teens. It's also a very beautiful film.
Chuck