I've passed by McAdie every time I've been up there so I can't offer any advice on that aspect of your trip, but...
... there is a chute on the "west" side of McAdie which doesn't look too bad. Once down off of McAdie, a high traverse over to Discovery Pinnacle and the Main Trail is fairly easy. Mike and I did the Marsh to Discovery portion of this traverse last Sunday. You can see what the terrain looks like if you look at our photo albums from last weekend.
Another question I can't answer is how long it would take to get back to the Meysan Lake area after climbing Muir. If you didn't double back "over" McAdie, you'd have to contour around to Crabtree Pass and then Green Pass to get to the LeConte Plateau. That's a lot of ground to cover on such short days.
(It took us about an hour to get to Discovery Pass. I'd add about another hour to get up Muir from there.)