How long is a piece of string ?
Hello and welcome to the RTA forums !
This sounds like a great way to celebrate your half and Qtr century milestones, but at the moment your questions are a little like "how long is a piece of string" Lol.
I love the planning stages and you have a lot of time to do all the dreaming and researching and I would start off by looking around the RTA site where you will find all aspects of visiting the US, this one thread has some great suggestions for the West coast.
You might want to tie the "best time to visit" to coincide with one of the celebrations and it is all subjective, but my favourite time is mid Sept through October when the crowds have gone, the temps are nice [especially in the desert areas and Vegas] and you will See some Fall colour.
How long, How long have you ? You could spend 3 weeks or 3 Months and not see it all.
It's too early to start mentioning possible places to stay out of the hundreds of thousands of options. Get hold of a good map, look around RTA and discuss the finer detail with your travel partners and when you have the basics sorted [time of travel, How long and some dots on the map] we can help you piece it all together.
Enjoy the planning.
Just too add.............
Eris has given you good pointers to get started, and as has been said, time will be a crucial factor, but with enough of it I would first head from San Fran to Yosemite, it is a wonderful place ! Another thing I would consider is to drive to the Grand canyon national park from LA and stay over and witness sunset, very romantic ! ;-) Then head back towards Vegas by road over the Hoover dam and a possible short diversion onto route 66 through Seligman on the way to Hoover dam.
As Eris commented, these are just pointers to get you going and once you have made a start on your plans let us know and we can help "fine tune" them.