Jay I just went 3 weeks ago with my friend Matt to cs 18 and we took our 7 and 4 year old sons with us. I would say that is one of the best in your selections there and here is why. If you take the Bote mtn trail then turn onto the West prong trail it is only 1.6 miles. Another great reason is the campsite is really large and you have a lot of easy access to the stream where it runs through the site. Other places like cs 39 the creek is not as accessible. I have been to cs 40 and it is by far the ugliest campsite I have ever seen in the smokies. I guess there is a reason to it being called Big Hemlock they apparently didn't treat those trees and most of them when I was there were felled down into the camping area. There was scarecely a spot to put a tent and no shade there now. I don't know much about 93 so someone else will have to help you there. Here is my trip report on our trip to cs 18:
We fished all over the west prong with our boys and caught many trout even right through the campsite area. Good point Pete on cs 65. Another one you could consider is cs 48 on Chasteen creek it is also just a mile in but I doubt the fishing would be as good as Noland or the West Prong. With a 3 year old you probably won't be able to wade up the stream but will probably just be fishing from the bank a bit I would guess.