This is one of the few places in Disney I would not take a child under the age of about 8 unless they were either very tall or very into video games. The height restrictions are the highest on property (Both Cyberspace Mountain and the BL Astroblasters have a 51" height requirement) and if they are not really into video games there will be next to nothing for them to do.
If you can give us a little more info on your situation we can give you a more accurate answer.