I would recommend you call and make the reservation now if you are planning to be there on a Friday or Saturday night.
Lots of locals (within a half day's drive of the Fort or so) make reservations well in advance for the spring and fall weekends (Friday and Saturday nights). The Fort is full to the gills on weekends and has some spots available on weekdays as a result. So if you wanted to include a Friday or Saturday night, don't delay. Given that it's still spring break for you and likely others, I would book it sooner rather than later also.
If DH thinks that's too soon, we better not tell him how fast it will fill up for Halloween 2017. The stampede will begin about a week.
Bama Ed
PS - that makes me wonder if Disney will close that opportunity for the 2-night weekend reservation. Given the new rules in place making it harder to drop/add nights, I wonder if the reservation system will not show availability for a Friday/Saturday 2 night reservation but would if you included a Thursday or Sunday night. I wouldn't put it past these guys...