Well this is finally coming up and we're just about set on our trip. Lots of thanks to this forum for all the info, I've been reading through the threads, it's really helped us plan everything out. I have a couple more minor questions but i'll give a quick overview of our itinerary.

After flying into Vegas we'll be hitting Grandview Campground near White Mountain for some star gazing. This is at 8k ft elevation.
Pick up permits next day and head to Horseshoe Meadows to camp, or, hike in a couple miles depending on time. Horseshoe Meadow at 10k ft
We then have 6 days to do: Cottonwood pass, to PCT, to JMT, to summit Whitney and then back to Horseshoe Meadow. ~60 mile round trip. Going to play it by ear as far as mileage per day depending on what our bodies are telling us.

On the way back I'm thinking we'll change up the trails and take Rock Creek trail over to Soldier Lake. Then, depending on how we feel and how much time we have, either hike into the Miter basin or, summit Langley.
We'll take New Army pass back through Cottonwood Lakes to our car on the final day. (final day needs to be short as we have to get back to Vegas that night)

So quick questions:
1. Temps? Our plan is to stay at Guitar lake the night before we summit, which would be our highest overnight spot. What can we expect for lows? The Mountain-forecast site and Timberlinetrails site give conflicting temps for 12k feet. MF says lows in low 50's, TLT says lows in upper 30's to lower 40's. The highs are also way off. Big difference in which bag I bring.

2. Water sources? I carry 3L with me always, how is the water flowing this year? I just got back from a 45 mile trip in VA where everything was bone dry from drought, not fun!

3. Can you swim in the lakes?

4. I've read a lot of people get up at 2-4am to start the summit climb. I like the idea of seeing the sunrise from the top, but otherwise we're not in a huge hurry. Is it worth it to avoid afternoon storms this time of year?

5. Diamox? We'll be camping at 8k feet, 10k, ~10-11k, and ~12k on the nights leading up to our summit day. Is Diamox still recommended?

6. GPS maps? Does anyone have recommendations? I use Guthooks for the AT and absolutely love it, but they don't cover all the trails we'll be on for this trip (rock creek, etc) and I'd have to purchase multiple different trails for what we're doing here (PCT section, JMT). I've seen Gaia recommended, worth the purchase price? I'd like to be able to load tracks into it for the side tails on our return trip. Reliability and offline maps being key here.

Thanks for any more details you can provide. I'll also try to provide a trip report when we get back.