If Magic Kingdom is open both at the time you are going and the time you are returning, the easiest way to get there is to go to Magic Kingdom and then take the boat to Ft. Wilderness. The walk from the boat dock to Trail's End is very short.
If you are going when MK is closed, it is a little more time consuming. If you have a car, you can drive to the front parking lot of Ft. Wilderness and park. ( Note, you will NOT be allowed to drive into Fort Wilderness. ) You can then take the internal bus back to the bus stop near Pioneer Hall. The Trail's End is connected to Pioneer Hall. Then after dinner, you return the same way to the front parking lot. A taxi would have to drop you off at the same parking lot. So you would still have to take the internal bus and then return by bus for another taxi ride.
You can also take the Ft. Wilderness transportion from any other park or Downtown Disney. But realize that this will be time consuming.
Maybe it would be to your advantage to make sure that you go to Trail's End when Magic Kingdom is open.