For large groups, consider booking an Airbnb as soon as you can find one available. Many will be live starting in the new year but June in Montana is a popular month. Please consider staying near downtown if you do not plan on having transportation. Everything you need will be within walking distance.
Bozeman has a few Ubers but do not depend on it. Plan to book rental cars in advance as the rental car companies often have trouble keeping up with demand and there are several weddings the weekend of June 16th.
The altitude in Bozeman is roughly 4,280 feet above sea level. Some people may be minimally affected but please prepare accordingly by drinking a lot of water on your day of travel. It is easier to avoid and get ahead of than to fix. Try and stay hydrated on your flight and drink plenty of water throughout the day and during any celebrating!
The reception venue was previously warehouse space and the floor is going to be concrete. There will be a few people directing parking when you arrive in the gravel lot next to the venue. Please try and carpool where you can. There is parking closer to the venue on a paved surface for anyone who has physical limitations. You will want your sunglasses as the sun does not set until around 9:30.