I've noticed that in manga (the traditionally drawn ones) word balloons aren't perfectly done, I mean if you look closely at the nib strokes, lines are shaky, not perfect. And that's what I like, it just looks organic. I've seen pros draw balloons as a 5 year old, like you say, and that's fine in my book, those perfect MS speech bubbles aren't quite appealing in my eyes.
A personal opinion here, if you're doing a scream balloon, a fear balloon, don't focus on the shape or lines too much, do a shapeless "balloon". Traditionally you would draw it more triangular, with spiky edges and all, but the thing is, if you draw it freehanded and using all the shakes and iterruptions of your stroke in order to create a more organic line, that line can convey better that feeling of fear, and nervousness that you're character is feeling. A balloon that represents that uneasiness the character is having. If you draw it with perfect straight lines it may create a little disturbance in the force (drawing).
That's just what I think Oo.oO
P.S: Also, checking some horror or guro mangas (if you're into that, like I am, cough) may provide awesome examples of those kinds of speech bubbles.