Again, thank you for all your help.

After careful reading all replies, I made two itineraries: one based on the feedback from AZBuck along with Mark Sedenquist, and another one based on Southwest Dave's post.

Option 1: AZBuck along with Mark Sedenquist

My doubt abouth this one is day #2 (21th april) and #3 (22th april).

On day #2 I'm leaving Las Vegas and want to visit the Grand Canyon.
If I go via Flagstaff it's almost 4 hours from Vegas to Flagstaff plus 1,5 hour each way from Flagstaff to GC. I think that leaves very little time to visit the GC.
I could go from Vegas direct to the GC and then stay in Flagstaff.

Day #3: Why go back the Grand Canyon village? I was there the day before, or not?
I think I could go direct to Cottonwood.

Day #4: Kingman or Wickenburg? Wickenburg is nearer? Is because of Route 66? Is it worth it, this section?

Option 2: Southwest Dave

I think I don't have any doubts about this one.

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Both seem to be quite similar on the miles covered and that's something important because, as I expressed, we don't want to be driving (almost) all day, day in day out.

Other thing that is important is choosing the most cenic/fun routes!

I made word docs for each one, with google maps links and prints, for each day.

Thanks again!