Thanks for all of the great thoughts so far. A couple of responses...
1. We live in the Bay Area now so Yosemite and Death Valley aren't destinations to stay for us, just places to pass through and we can catch those some other summer.
2. Likely just do a drive through of Yosemite Valley and Tuolumne Meadows and camp for the evening near June lake just South of Mono Lake. Even though I could make Vegas in a day from the Bay Area, it's a sucky drive going through Barstow and I think a quick way to kill enthusiasm right out the gate. Taking the scenic route through Yosemite and Death Valley add a day but give us something to enjoy right at the start.
3. I've driven through Death Valley several times before and from my experience, it's not a destination either but something more interesting than I95 through Nevada to get to Las Vegas. On the other hand, my truck is a 99 7.3 Diesel and I will be hauling camper plus cargo trailer. Most likely would not have a problem but I'm not sure if it's worth the risk of passing through in the middle of July with new borns.
4. Las Vegas is where my oldest daughter was born and she hasn't been there since she was 3 years old. We've talked about taking her back to see where she grew up (still own the house). If it wasn't for that I agree it wouldn't be worth stopping at but it is on the way if I want to go to Grand Canyon so it's more of a "why not" stop.
5. Grand Canyon I'm not sure if I want to go for North Rim or South Rim. I've read that North Rim is less busy and cooler so that seems like a plus for summer time. South Rim seems to be more touristy and we get the bonus of going over the Hoover Dam. I'm not a huge desert fan so taking the southern route looks to be boring and would just add miles in my opinion unless there is just something we "have to see" on the South Rim I think I'm leaning on North Rim.
6. The drive from Grand Canyon to Grand Tetons looks to be ~675 miles. This we will need to break up into a least 2 days. Split in half we would need to stop on the southern end of Salt Lake City. Is there anywhere of note to stop for a night in this area?
7. Looking at staying in Yellowstone a full 3 nights (two full days). We won't get to see everything of course but hopefully the highlights.
8. The drive from Yellowstone to Glacier National Park is 550+ miles so we will need to either suck it up or breakt it up.
9. Glacier National Park to Seattle is another long haul. Is there anything worth seeing around Spokane that is worth adding a night to break up the drive?
10. Olympics / Oregon Coast I've done before and have a pretty good feel for it.