Hi and welcome to HT!

I shall move you post to our America forum where it may get a better response.

luci

I think you will find that every traveller has his or her favourite National Park, whether it be in the USA or anywhere in the world, therefore I wouldn't be overly concerned with which is best, and in my opinion you really can't go wrong with any of the major (or minor in most cases) NP's in the USA.

If you are up for the travelling then it sounds like a good trip planned. Be wary of August prices though and if you have options to travel at other times certainly consider them. I put off a 2 week trip through South Dakota, Yellowstone, Grand Tetons and the Rocky Mountains last August due to cost implications. I am happy to pay over the top at peak periods for decent accommodation but when you are looking at $200+ for a Motel 6 or Super 8 OUTSIDE of the parks (I think it was West Yellowstone) you really have to reconsider your options. In the end we went for a great trip through New Mexico (Albuquerque, Santa Fe and Taos) paying $60 a night in Albuqurque and $39 a night in Santa Fe, before heading to Vegas to win some of our trip money back.

If it has to be August seriously start thinking about booking accommodation. These places fill up fast, especially lodging inside the parks and I found that any city or town near any of the major entrances to Yellowstone for example also sold out fairly quickly, and if they hadn't it was very expensive. Flights might also be top whack at this time of the year as well.

Personally I love Yosemite NP. It's such a great place, lots of treks available, jaw dropping scenery. You name it, Yosemite has got it. Lodging is not cheap, but we found the Curry Village site inside the park a good option, rustic, no frills (heated cabins and static tents with or without bathroom) but at $100 a night it was certainly more affordable then some of the more "luxury" accommodations available. Some people have a major gripe with the facilities available but I found them to be ok, a couple of restaurants, a food court, shop selling supplies etc. If it's wet, it's not pleasant but August should be fine. You also have the option to stay outside the park and drive in every day, a lot of people do this but for me the excitement of waking up in Yosemite beats any motel experience outside the park, and sometimes savings aren't as huge as you'd think. Definitely worth looking into now I would say. I think the company that runs accommodation bookings in both Yosemite and Yellowstone (definitely) is called Xanterra.

Keep us updated with your plans.