Yes it is every night. It is called the Sing a Long and movie or something of the sort - more info, including the movie schedule (at the beginning of each month) can be found on the CAMPING board.
It is a lot of fun - have done it 3 times - there is no cost but there is a snack cart there where you can buy the makings for smores and then toast them at the fire. The sing a long can range from great to so-so and then the movie is fun.
If you do not have a car and aren't staying at Fort Wilderness - it does take awhile to get there - so be prepared.