Dear all.
Thanks for all your great info and comments. Just what I hoped for, and it definitely got me thinking. Among other thinks I took the following from your comments: set aside ample time for each visit to the NPs, consider a loop and, well, even more interesting places were mentioned. So, now I am thinking that whatever we do, we need to come back again. And since we are travelling with small children, it's important to us to keep a pace that they will appreciate as well. None of us will enjoy it if the kids feel they are just being tagged along on a trip set by and speaking to only my wife and I. Hence, this new idea that takes all of the above into consideration: fly into Vegas and continue to Grand Canyon - Bryce - Zion - Lake Tahoe - Yosemite - Kings Canyon - sequoia - west coast - SF. It should make it a shorter trip in miles, leaving both more time for each stop/visit, and shorter distances between each stop, zig-zagging further west. It hurts me (!) not to be able to visit Badlands and especially Yellowstone, as this was something I personally has been looking forward to, however, we could then come back in a few years and do a Denver loop, visiting The black mountains, badlands, YS, and even ad Arches, Moab etc.
Any thoughts on the above are welcome! Looking forward to hearing from you again, and again thanks for all your initial and very quick responses.