Assuming all the paths are in the same order for both group elements you're wanting to morph from/to, you could loop through the children of the group element like this... This is intended for paths only.
var TL = new TimelineLite();
var pathsBefore = document.getElementById("g-before").children,
pathsAfter = document.getElementById("g-after").children;
for (var i=0; i < pathsBefore.length; ++i) {
TL.to(pathsBefore[i], 1, {
morphSVG: pathsAfter[i]
}, 0)
}