School Holidays in Australia in the latter part of June, may have some impact on your choice of accommodation, but I doubt Cairns would be completely booked out. Perhaps contact the places you like & see what they think.

http://www.takeabreak.com.au/HolidayDates.htm

Pat W's a regular & authoritative poster who lives in the area - she'll have a better idea than most.

I think you will be safe in using Wotif in June...certainly not the busiet time of the year by any sretch of the imagination on the accommodaton cakabder,,,at least in Australia which is what I'm competent to comment on. Wotif offer accommdoation 28 days out, so you can start making your choices in May which will give you heaps of time to make other arrangements should you feel you are not getting the choices you want on www.wotif.com.
Have fun

It's fairly unlikely that you'd have accommodation problems in Cairns in June. July is a different story, that's when it starts to fire up here with combination of North American and European tourists on their annual leave plus Australians from southern states escaping their winters. Not to mention our Kiwi neighbours, although NZ has a small population, Kiwis comprise a large portion of Cairns' tourism in our "winter".

We returned recently from a short trip to south island NZ at the end of March.

We did not have reservations for one night in Invercargil- arrived at 6 PM and found every motel booked. We were advised to drive an additional 2 1/2 hours further to Te Anau, which we did , to find accomodation for that night.

I must say the folks at Balmoral Lodge Motel in Invercargil were extremely kind and helpful- they were on the phone and computer for a good 20 minutes trying to help us find a room for that night.

I would suggest you have every night booked before leaving for your trip.