Some excellent points already made.
I flew the length of Death Valley last week. It's interesting at the moment because part of it is flooded!
It's true that it is surrounded by MOA's but the airspace within the valley is excluded below 3000' (Please be sure to check your chart on this). You are 'requested' to remain 2000' above the National Park (defined as the highest ground within 2000' of the aircraft) so you have a slot of 2000-3000' to cruise along. This is just as well since there is not much radio contact in the valley itself. You do have to cross the MOA to get in and out and radio contact may be a problem, but there is an FSS frequency at Furnace Creek and as said before, the MOA's are not restricted airspace. There's an article on MOA's in the current AOPA Pilot.
Regarding the Archer with 4 up (and presumably baggage), I wouldn't do that even at winter temps. Is it even permitted with full tanks in the w&b? I've actually witnessed 4 Brits turn up at an FBO in Vegas in the winter expecting to do this only to be told they need 2 aircraft or a twin.
Sedona is second nature to a UK pilot used to short runways and awkward approaches and a doddle compared with, say, Perranporth which is also on the edge of a cliff. But again, 4 up in a 180HP is marginal at best.
You don't need Oxygen in the Grand Canyon VFR corridors. Look at the special chart, which hasn't changed (unless I have this wrong) in about 10yrs or at
National Park Service . I've been up to 11,500 but never 13,500. There used to be a chart with photo's of the landmarks on the back but I don't know if it's still available. I have a description at
my own site .
Appropo of the above, I wouldn't fly this trip now without at least a hand held GPS. Even the cheapest will allow you to enter the exit/entry points you need. (But I did fly this terrain repeatedly before I had a GPS!!). My own technique is to use the GPS as a cross check for conventional navigation, because identifying surface features is what VFR touring is all about.