HISTA is our least favorite of the 3-D shows. It is also quie loud. We just don't like the story all that much. IF your child is afraid of snakes they probably won't like it. If they aren't afraind of snakes or loud noises then they might be okay, espcially if you can warn them about it ahead of time.
Bug's Life seems to be the worst for little kids.
I would do C B Jamboree, VotLM, Muppet vision 3-D, and/or Philarmagic first, if you can, and see how those go.
It always helps to give kids a heads up, tell them there will be noises and water squirts. It also helps to have the child sit in your lap. That way they won't feel the special effects in the seat. If you can figure out where the water squirts from (Look at the seat in front of you) and block that spot, then that will also help reduce the shock factor - though the child might be wondering why everyone else is reacting. The child can also always reduce the effects by taking the glasses of or closing their eyes. Maybe try going in without the glases, and then again with them. I think part of the fear factor for many kids is not knowing what to expect, if they get a partial exposure, and then know wht to expect, they will most likely face the attraction (and others) the second time around with less concern.