Rain wrap for the Sierras: I can only say that my experience was just one afternoon of rain in that ~300 mile stretch, and only a couple of days of rain (tops) in all of California. It can surely vary of course, but still. So carry it for the Sierras if you're inclined, and get it when you get your bear can and mail it home when you get rid of the can. Don't carry it throughout CA !
Sticks for a digging a cathole: I politely request that you dig your holes deep enough --- you know the discussion threads about this, please let's not start another one, but IMO "finding sticks" isn't always going to cut it when you "need to go now". The ugly truth is that there are always more rocks and more roots whereever one tries to dig than seems reasonable. I personally use a sand/snow stake which is dual use as ... a stake. Some make do with the tip of a trekking pole, but this can be challenging sometimes.
40' of cord seems like plenty to me depending on exactly what you anticipate doing with it (I won't even raise the whole bear/food-hanging issue, as what most thru-hikers do outside of the Sierras raises eyebrows among those discussing it at home ...).
Sunglasses: definitely take them. Definitely take them! Have a good pair in particular for the Sierras. If you don't want to buy sort of low level glacier glasses, make some side shields out of duct tape.
If you visit your optometrist and they dilate your eyes and give you a pair of those fashionable folding cardboard-earpiece sunglasses, take a pair of those *as backup* in the Sierras as you definitely want sunglasses (FWIW, I did manage to lose a pair of sunglasses in CA).
Sending items to different sections of the trail: For the Sierras you have to make some adjustments, if only to get and return the bear can, and most folks would suggest an ice axe, though if doing it again, I'd use a black diamond Whippet as one of my poles, and in fact will carry one to start the CDT this year. I'm still going to mail it back home after I'm done with the worst of the snow (it's quite heavy for a trekking pole).
I agree with Dirk on the light source thing; I normally carry an e+lite, but would upgrade to something beefier if I anticipated night hiking; you might therefore consider a higher candlepower headlamp to start the trail (the first 700 miles is when you'll want to night hike, if at all, due to the heat), and again --- swap for your e+lite when you get your bear can at Kennedy Meadows.
Note that if you're carrying an e+lite that you may have trouble finding those coin-type batteries in a lot of trail towns. Due to that plus cost, I bought a bunch of them online ahead of time and included replacements in resupply boxes.