Should be a good trip. I think 5 nights ought to get you through just fine, even if you go the PCT-JMT route.
If you are strong, you could do Langley the first day, but you would need to start out pretty early. ...or start out the afternoon before and knock off the first few easier miles and then camp.
Two years the switchbacks were accessible late: 7/9/2011 and 7/1/2010. Since then it has been in May. I would plan on the trip, and if there is heavy snow, just descend about 2 in the afternoon when snow is soft, and either glissade (take an ice axe), or plunge-step down the snow slope.
BTW, you will not be allowed to park your car at Whitney Portal for that trip, due to all the road construction.
I am hoping to do a similar trip, late June or early July. I definitely want to go over Crabtree Pass to try some fishing, but I want to also head down to Crabtree Meadow and below to the hidden packer camp a mile west of the PCT -- I've been told there is a spring there that may be warmer than normal, so want to find it and see.
