Port Douglas - budget accommodation options?

So friends are getting married in Port Douglas in September - we want to go, anyone any recommendations for budget accommodation for 2 adults 2 children? Not sure how long we will go for yet - maybe a week - depends on cost - e.g. if a week is cheaper than per night we may do week.

When I say budget I mean we are quite happy to stay in the YHA with 4 of us in bunks in one room - but only if that is the best deal.

Any must-do's - we have been before as backpackers so have some recollection of the area.

Also any opinions on what length of stay would be viable, with a 4 and 2 year old - I am thinking a dash up just for a long weekend might seem like an ordeal - wedding is on the Saturday.

I have liked a page on FB called Port Douglas units in the treetops. They often have really good deals, the last one I saw was 50% off. It's worth following them.

Cheers -have followed

I have now sorted accommodation and flights - I am assuming that a car will be useful??? - the cost of just getting too and from the airport seems to be about 2/3 of a hire car. We have 3 full days there not including day of wedding - any things must do with a 2 and 4 year old (we will do the train and sky rail at Kuranda one day - as DS and I are train lovers - and DH and I did it years ago and loved it).

Get a car. Definitely.

When will you be up? Would love to meet you if its possible in your time frame.
And Yes to a car. The city of cairns is boring as all hell so you need a car to get to the good spots!

We are up 4th to 9th of Sep - there are a few people going for the wedding which is on the Sat so no idea if we will get much free time yet or not - but will let you know Efjay.