Your bro is getting married and its time to celebrate. Sure, Boise is known as a "hotspot" for family activities, and there are plenty of breathtaking places to explore the great outdoors. But you're looking for something a little different. After all, this is your best friend, you two have been through so much together. Moreover, it would be unjust to send him down the aisle without throwing an epic bachelor party.
Reddit user Buckwheatios was in this exact situation and asked:
"Hi, I’m one of my friend’s groomsmen for his upcoming wedding in February. Can anyone shoot me some ideas for a bachelor party? I thought about a trip to Bogus then maybe barhopping downtown."

Idea 1 from Reddit User Halfflip: Air BnB & Bar Hopping

Image via Google Maps
There are a lot of cool places you can rent for a night in Boise, cabins included. Cool mansion style homes you can go wild in. Check airbnb.com. Bar hopping downtown is the best bet. You can set up a scavenger hunt at a few bars, get with the bars earlier. They would be happy to do it because it can involve shots. Just some ideas.
Idea 2 from Reddit User Tachikomaz: VR Arcade or Escape Room
Swillklitch
For his bachelor party, my husband's groomsmen took him and a few close friends here to a VR arcade and they had a blast: https://www.vr1arcade.com
We have done an escape room with some friends, and I think it would make for an enjoyable and bonding bachelor party: https://escapethisliveboise.com

Idea 3 from Reddit User Apostle0: Paintballing

Getty Images
A buddy of mine was best man for a mutual friend and scheduled a big paintball game with the groom and all the groomsmen (plus some other close friends). It was a lot of fun.
Other suggestions included:

Boise Brew Bus
Breaking Bad Themed Bach Party
The 44 Club
The Whisky Bar