Use the extra wood to make a homemade bow, that's always a fun side project. Im sure someone more knowledgable will be along promptly to let you know about safety as I don't have a clue at the moment.
I'm sure I read a huge long safe/not safe list of plants and wood and saw that Birch and Silver Birch are safe. Damned if I can find what forum it was on though. We gathered wood from our local forest, made sure to identify it (google pictures are useful) and then bleeched the hell out of it, baked some parts, removed bark and let it dry for several days.