Make each kid find a place they want to visit. Use that as the outline.
Frankly, Key West is more interest to adults than kids in my opinion - and better beaches at Panama City, Fort Myers, even Daytona.
We made a three month trip last summer from TX to AZ. (We have a granddaughter who lives with her mother in a north Phoenix suburb. Messy angry divorce. Our choices to visit her were limited.)
NM is a big question mark for 2021 IMHO - we had them cancel several state park reservations - and cost me $70 in lost reservation service fees.
Folks on another forum taking about current CA RV quarantine. You can go through the state, staying 1 or 2 nights in a CG, but to explore, you need to stay 14 days in self-quarantine in the first camping location in the state that you visit.
I would not plan to go to that state in 2021. Maybe not AZ, and it was HOT. And at 114 degrees, I don't care if it is dry heat - it is an oven.
Joke in Texas is that if you want to camp where Texans do in the summer - go to Colorado - over 5,000 ft elevation.