I will be spending 5 days in Cairns, and doing these day tours - Great Barrier Reef, Daintree, and Chillagoe Caves. Also doing Hot Air Balloon on the last morning. Now for one remaining day would you suggest Atherton Tablelands or Kuranda Scenic Train and Skyrail? I'm confused, so any suggestions welcome! Thanks in advance!!
Check your dates that the train is running, it only runs on certain days. You don't have to do the train to do the Skyrail, they can pick you up in Cairns with their shuttle bus. The Skyrail to Kuranda takes you over the rain forest with some great views, and Kuranda is a touristy village with some nice things to do for an hour or two.
The tablelands are exactly that, a large area of tablelands on a plateau about 60km west of Cairns. There are various tours there, you can see a large fig tree, waterfalls, nature walks, lakes, or old time villages.
I'd probably opt for the Skyrail as it might be more unique.
The Skytrain and canopy walk is briliant - so are the Atherton tablelands. When we were there we took the skyrail and the walk up to Karunda and then the Baron Falls train back down into Cairns - enjoyed the whole day. The Tablelands were good for a drive around and potter about but I think the skyrail thing is better.
I realise you are going out to the Barrier Reef but another great day trip from Cairns is the boat out to Fitzroy Island for the day - a forty minute journey and then a full day on the island a few miles out from the mainland - great snorkelling and almost as good as the Reef much further out.
Mossman Gorge is good for a couple of hours walking about - good wildlife.
I'm not sure about the scenic train, but the waterfall and rainforest walk is very nice. If you have a car, you can access both these things by just driving up the mountain. Don't go too late in the day if you want to walk around Kuranda. All shops pretty much shut after the last train leaves.
You could easily drive up to see the waterfall (it's an absolute stunner!) and then spend the rest of the day exploring around Kuranda and the tablelands. I'd definitely recommend making the waterfall a priority though, whether by scenic train or not.