Our trip in November 2016 we will be checking in on November 24th and checking out the morning of December 2nd. This is 8 days at the campground. We will most likely get 5 day tickets (we also like a day at Sea World) but even at that we may be thinning it down to a 4 day. If you have a SOLID 2 weeks at the Fort (not including travel time) then I would Agree with PaHunter that you may want more. My kids are older and able to do a full day (mostly) in the parks if we chose to do so, however, being able to do 1 day starting at RD and going to early evening and then another day starting at early after noon and going to closing might be worthwhile to see the different things. (Don't get to see the fireworks/wishes during the day). I will say, however, staying to close may make it so you want the next day to be a "Down" Day at the Fort (or for a slower day maybe at Disney Springs or whatever...)
Being able to add on days (before they are all used up) is also a good option. For us, however, I don't think the water park would be worth it. Although our DD10 really wants to do it, we have heard too many stories and problems with the Waterparks, coupled with the fact that we cannot expect good swimming weather in November/December.
Either way, I am sure you will have an awesome time and your 4 year old will make memories to last a lifetime (as will you).