We are staying at Evergreen Lodge on the west side of Yosemite and are trying to decide whether to try and make Las Vegas in one day, whilst trying to also stop for a short while in Death Valley!
We are travelling in August, so I assume the Tiguna Pass will be open!
Any ideas on timescales?
Also if it is to far to travel (with 3 kids) in one day, can anyone reccommend somewhere interesting to stay around half way? (I have tried the Furness Creek hotels but they are all fully booked)

I think you mean Tioga Pass. That is really the best way to go to Vegas because no road crosses the Sierra Nevada for a long ways to the south.

You may need to find a place in Lee Vining near Mono Lake, but it too is a popular place.

The road from Lee Vining to Vegas was not heavily traveled the last time I was on it until near Las Vegas.

The road over Tioga Pass is a piece of cake. The first time I drove over Tioga, it was a thrill because the road was narrow and winding. My dad (now gone) and I thought all the fun had been taken out of the trip when the new highway was completed.

However, the traffic volume dictated modernization. There was change. But, was there progress? Depends on the criteria. At least it was safer.

From the west side of Yosemit to Las Vegas would be a very long nasty hot day in August.

Look at mapquest for more details on the time it takes. You will miss out on a great deal of the beauty of Tuolumne Meadows and the eastern Sierra trying to do this in one long day.

Death Valley will be really, REALLY, horribly hot in August (so will LV, but not to the same scale and there is more a/c there than just about anyplace on Earth)

You really won't be able to get out of your car in DV - so I would concentrate on the northern bit of that trip and explore Tuolumne Meadows and some of the back side of the Sierra and stay the night somewhere - Mono Lake or Bishop or in between. Then the next day high tail it through DV and on to LV........

Unless you like REALLY HOT and REALLY DRY climate, follow the advice of janisj and see DV from the confines of your air conditioned car. Spend your time in Lee Vining, Mammoth, Bridgeport, Bishop or Lone Pine. I live in the desert less than 100 miles away and wouldn't dream of going to DV in August unless I had to!
If you try to make it in a day, you won't have time for anything beside a drive through of any of the places, including DV.

I can't believe the Furnace Creek Ranch is sold out in August. Nobody goes to Death Valley in the summer except crazy foreigners and people who go there to test new cars. I would call to see what the deal is if you want to try and stay there.

Otherwise, I agree with the other posts about spending more time maybe around Mono Lake or something, and then you could drive through Death Valley the next day on the way to Vegas.

In Death Valley it will be so hot that you'll have enough time to snap a picture at Badwater Basin and then you'll need to get back to the car. But if thats what you want to experience, go for it!

The fastest route would be to take Tioga Pass to Tonopah, then down Hwy 95 to Las Vegas. Just this drive alone is 406 miles and will take over 9 hours of driving time. This could be made in one long day.

If you really want to drive though Death Valley, I think I'd spend the first day taking my time driving though Yosemite and enjoying the high country and spend the night in Tonopah, NV approx. 200 miles from Evergreen Lodge. Next morning, take Hwy 95 south to Scotty's Junction and enter Death Valley this way. I doubt you will be getting out of your vehicle in Death Valley. Take 178 and 190 thought Death Valley, then head back to Hwy 95 at Death Valley Jct. The second days drive will be 277 miles.

Just make sure to carry drinking water and make sure your car is in top running condition. There is NO cell service in Death Valley!!!!

Utahtea