Green Cay has two boardwalks - 1 mile and 1/2 mile. I'm usually there about 2 hours. The nature center is open Wednesday through Saturday. I think it opens at 9am, not sure, since I'm gone before it opens. The park opens at 6:30am right now.
Wakodahatchee is 3/4 mile from the parking lot. Loop is 1/2 mile. That can be done in 1 hour if there's no wildlife. No nature center. Opens at 6am right now.
Loxahatchee has loads of trails - grassy berms, one boardwalk, fishing pier and a boat ramp. You can also rent canoes and kayaks. The Marsh Trail and the Cypress Boardwalk are the most popular. Not sure how long it is. If you use the Lee Rd entrance there are usually Black Hooded Parakeets there. A flock of Monk Parakeets flew over a couple of weeks ago.
Currently Green Cay has more to see than Wako.
I have Black Hooded Parakeets in my yard all the time, especially when there are loquats on my tree.
This is from Loxahatchee (made BirdWatching Magazine Photo of the Day back in March).