Knowing what I know about the series I think I would be able to arrange a much better outcome.

Ian McKellen doesn't have to chose. He's also Magneto, so he's really kick-ass.

The last question I was asked was whether to have a shower or have to choose and follow my choice for the next question, which is this one. I AM Gandalf now.

Gandalf is actually a Maia, a powerful supernatural being that's basically an angel and that cannot be permanently killed. They serve higher beings but seem to have a heck of a lot of latitude in how they go about their lives. Sauron was also a Maia, for example.

Dumbledore's just some guy who couldn't come up with a better plan to stop Voldemort than deliberately getting killed while manipulating an annoying inept child into saving the day and getting all the credit.