Iceland in August/September
 

Hello fellow Fodotires,
I am exploring an option of going from NY to Iceland for 5-6 days at the end of August/beginning of September.
Questions.
1. How is the weather down there during this time?
2. Northern lights - will we be able to see it?
3. We usually travel very actively but this time we would like to take more relaxed pace. Is there a place where we could relax for couple of days without being bored? I am picturing a place like Blue Lagoon but may be more cozy, less commercial, next to a cute town. Any recommendations? Something not far from Reykjavik.
4. If we spend 2 out of 5-6 days at the spa how should we spend the rest of time? It's our first trip to Iceland.
Sorry if the questions are basic, I am just at the beginning of planning.