As usual the retired crowd screams you need months to do that trip. I have been to every place on your list way more than once and I'm not retired. Both of my kids have been out west(and it's a drive for me, PA)
At 23 and 27 they still want to travel with us and the older one is already looking for her own RV.
Take the trip as planned and have a great time, your kids will love it and talk about it forever. Mine still do.
Older one is considering doing a trip for the honeymoon this fall. When your not retired sometimes you have to push it a little. I did Alaska in 5 weeks from PA. Awesome trip, but I was told it couldn't be done by ,many.