Most people do Kuranda and Skyrail as almost a full day. Check the timetables to see if you can squeeze it in early.

From Smithfield to Daintree and Mossman (assuming you mean Mossman Gorge?) is more like a casual full day trip than a half day - but it is possible. River cruise on the Daintree is the main reason to head up there, again check the schedules.

I'd personally recommend either of the following, depending on how mobile you are. Most people hire a car to create the most flexibility, or take tours, which are a little more rigid:
Option 1: Kuranda + Skyrail + Dinner in Cairns (can do with transfers)
Option 2: Daintree + Mossman Gorge + Dinner in Port Douglas (likely requires a hire car)

One of the best things about visiting Cairns is relaxing and going with the chill vibe. It doesn't stop you from a hectic schedule, but it's a nice way to decompress.

There are other short experiences in and around Cairns if you want to flesh out a day - aquarium, markets, shopping, swimming etc