Yeah its possible. The best thing is if the children div's will have a unique class name. In your case each div has a diffrent class name (message1,message2..), best thing is to give them a common class name, and then staggering them. But if you know that all of the child elements are messages you can easily do something like this:
TweenMax.staggerFromTo($('#message-container').children(),0.4,{alpha:0},{alpha:1},0.2)
here's a codepen:
http://codepen.io/bazooki/pen/avits
Hope this helps =)