We highly recommed to book an accomodation as soon as possible – June is high season in Interlaken.
Interlaken has a wide range of hotels in different categories.
Here are a few recommendations for group accomodations (besides Airbnb):
Prices start at CHF 48.00 pP (group accomodation for 6 persons, shared toilet/shower on hallway) up to CHF 61.00 pP (4 persons, shower/toilet in the room)
breakfast (all you can eat)
sheets (all beds made up) and a towel
private lockers in all rooms
use of self catering kitchen: 24 hours
high speed WiFi in the whole building and all rooms
free entry to public in- and outdoor swimming pools
free Minigolf and Tennis
free use of public busses