First time WWOOFer - allay my anxiety!

Okay so I'm planning to fly to Bergen, Norway next weekend from London. I've arranged to WWOOF for one month in the Western Fjords.

I'm beyond excited.

Here is my fear: I'm traveling on a US passport, and even though I have the right to be in the country as a tourist for 90 days without a visa, I'm still scared about being questioned by boarder control, and ultimately turned away.

I plan to say I'm traveling but don't know how much they will question me?

If anyone has WWOOF Norway experience as a non-EEU person, please let me know.