Are you confident riding deep powder? I know I wouldn't think twice about booking for the 5 run package. Even that sounds pretty light. How much vertical are they saying you are going to get?
You are going to be riding "wild snow", not resort terrain on a powder day. It will be snow that has seen minimal human impact. Of course weather and such has a huge effect on how the layers under the powder (which you'll hopefully have) are set up. It can be anything from fairly solid to almost non supportable as soon as you get out of your bindings.
Can you and your buddies just book the 5 run package for your group only. Helicopters don't carry a ton of people?
Also, do they have an option to buy extra runs?
The Selkirks are a world class range no doubt. Should be a fun experience.