Chanced upon Navette's service in the hostel and decided to book their trip to Mont Tremblant National Park. It was the best option I've found, as National Parks are usually inaccessible if you don't drive, and the price was really fair.
Proceed to book online, process was easy and confirmation was instant. When I have questions, the staff at Navette responded promptly either via call or email, it was amazing.
One day before the trip, Navette sent a reminder email with the meeting time, place and practical tips that is helpful for the trip. The bus was there on time and left on time as well - both for the departure and the return.
Will definitely seek their service again if I'm visiting another National Park!