Trail's end is a buffet for breakfast and dinner
menu here
http://allears.net/menu/menu_teb.htm
For lunch they have an ala cart menu
http://allears.net/menu/men_traillunch.htm
We have always really enjoyed it for any dining choice. And we have really enjoyed the lunch menu very much a couple times.
At lunch the place is pretty much empty.
The buffets are pretty busy though and you should make a reservation.
It is one of the more reasonable priced restaurants at disney for cash paying guests as well.
There are a few things to do there...walk around, look at the general store, there's a Circle D ranch horse barn that houses the Disney working horses and also has a lil nook of a museum of Walt's horses (free). There are also horse drawn carriage rides and wagon rides, and horse riding depending on when you are there (for a fee).
I don't know where you will need to be after your visit to the Fort but make sure to leave PLENTY of time for travel.
Keep in mind that you can get to the Fort by bus but it is an exceptionally long wait for Disney buses there.
If possible, I'd take the boat to Magic Kingdom and then go on bus, monorail or whatever from there so it's faster.
Make sure you alot for an hour to 90 minutes to get to and from the Fort...especially if you use the buses for your transportation.