Yes, I would suggest applying a gradient material to the group. Make the top attribute 100% transparent. Leave the bottom attribute untouched.
Apply the material to the group and adjust the gradient material shortcut on the model so the transition is to your taste.
Then translate the material shortcut in the model down until the whole group is transparent.
Make a new percentage pose.
While the pose window is open, there will be a new temporary Action in the Actions container. This temporary Action allows you to animate any group or material properties in the pose.
Click on the "Show More Than Drivers" icon next to the temporary Action and drill down until you see the gradient material.
When the Pose Slider is at 100%, Translate the material up until the whole group is visible.
If the group has any specularity or ambiance, you may need to slide the Pose Slider to 0% and set the Specular Intensity and Ambiance to 0%. Then move the Pose Slider to 100% and set those properties to their original values.
This is hard to wrap my head around. can someone make a quick video tutorial?