We have booked at the Mantra Heritage, the cheapest way we have found with manta accommodation is joining as an Accor member (it’s 5% discount and free to join) and to share a 2 bedroom apartment.
Due to Port Douglas being a destination venue, there are several Air BnBs and hotels in the area. We would recommend everyone to check their location of each venue to ensure they are not too far from the city Main Street.
I would recommend booking sooner rather than later due to being the high season of school holidays and very popular.
Port Douglas is located about an hours drive from Cairns. You will require to catch a lift with another guest or hire a car - the trip is a beautiful scenic drive though!