I've been down over Valentine's Day twice. We didn't stay at the Fort though. (At a conference both times, camped off site, Tropical Palms, and at the conference hotel the other time) We did go to the Fort both times.
The Fort was pretty quiet. The parks were crowded on holidays (President's Day and Valentine's Day) and the weekend, but other days it was great! There are more winter events now. I'd have to look at the calendar to see what is going on in early February. They will drive up parks attendance, but not as much at the Fort.
Weather can be a crap shoot. Plan for anything from 40-80... And maybe on the same day.
. One trip is was cool the whole trip. Upper 40s in the morning. Highs in the 50s to mid 60s. The other trip it was great. Upper 50s-70s the whole time.
j