The main way we have chosen to differentiate is to provide choice.  Similar to the building of a RAFT activity, we will be giving our students a menu of items to choose from.  This will allow children to easily self differentiate.  We have found that those who need a challenge choose it on their own.  Those who are not up to the challenge can choose less intimidating choices.  In our experience, giving an element of choice has been a very effective way to differentiate.  I know I am really looking forward to sinking my teeth into this project!