Hi, I have epilepsy and I got a PR visa, they didn't even question it, so I'm sure you will have no problem with your child. I really researched this an apparently they are looking for more serious conditions. Don't get me wrong epilepsy is serious to us but it can be controlled with meds so they are ok with this.
Just on a side note, epilepsy meds are not cheap here so just a heads up with that. Also, there's lots of support groups here if you need any help etc.