Tons of questions...if you don't mind...
DH and I have discussed driving cross country several times, but just don't know how to make it work...
DD13 has aspergers and doesn't like change alot...BUT... adores horses so this sounds so wonderful.. what was it like? How much were you able to ride..
THe driving wouldn't be bad, we usually drive to Florida from upstate ny and have no problems, between Her nintendo and kindle, hours can fly by without any problems....
This is our trip costs (2 adults/3 kids)
Boston to Phoenix Flights $1,550
Rental Car from Phoenix $500
Sedona I love Sedona!!!

Time Share for a week in Sedona (we only stayed 2 nights) $297
M Diamond Ranch Cowboy Breakfast & Horseback Ride $260.87
Pink Jeep Tour (Broken Arrow Sunset Tour) $371.60
Grand Canyon
Check in at Yavapia Lodge at the Grand Canyon $163/night
Jr. Park Ranger Program: Free
Shuttles all over the South Rim to different points: Free
Dinner at El Tovar $150
New Mexico -we stayed with family so no hotel costs
Albuquerque Balloon Fiesta
Glowdeo & Fireworks $10 parking & $8 per adult kids free
Special Shapes Sunrise Rodeo $10 parking & $8 per adults kids free
Sandia Peak Tramway $20 per adult & $12 per child
Petroglyph Nat'l Monument $1 Parking Fee
Santa Fe
El Rancho de las Golondrinas (Josefina's ranch from American Girl stories and doll--my daughters really wanted to go & all of us loved it!). It is The Williamsburg of the Southwest $6 per adult kids free
We clearly did A LOT in a short time and I wish we had more time at each destination, but we didn't, so we made the best of it. No regrets. I loved the Grand Canyon. When we go back to Arizona, we will devote at least a week to see more of the state. We did not walk down (not even part of the trail) into the Grand Canyon due to high winds and snow (! first week of October--this is atypical for the South Rim). We weren't prepared for hiking with 3 kids on trails with snow/winds, but we hiked around the top. My daughter literally bumped into an elk when walking from the restaurant with her Dad to the gift shop. My husband thought it was a statue...until it moved

. Sedona took our breath away with the beauty. It was so much better than I could have imagine even after looking at pictures. DH are quite serious about retiring around there. We went to the M Diamond Ranch and it was spectacular. The trail ride is a very slow, gentle ride and was perfect for my children and us. I think we rode about 2 hours--definitely enough for this Mom and kids

. When we were there they told me they are opening overnight accommodations for a full ranch experience, which would be so cool for kids. It was clean, the horses were well cared for, the food at the cowboy breakfast was yummy. I hear the dinner is even better.
The beginning of October was a great time to go (we planned it around the Balloon Fiesta and the kids had a couple of days off from school that we extended).
We wanted a room at El Tovar or Bright Angel but they were booked full. I was worried about Yavapai Lodge (thought it would be too rustic) but the room was very nice, newly renovated, eco-friendly with nice bamboo floors, nice tiled bathroom, and it comfortably slept 5 (!)
I hope this helps you decide. I could never drive across the country---not for me, but flying to Phoenix & driving to Sedona (about 1.75 hours from the airport) & then 3 hours to the Grand Canyon (maybe less, but we stopped to see some beautiful views). It was then about 8 hours to visit family in New Mexico. The kids were fine. We were all pretty fascinated with the scenery (so different than New England). It was a lot of driving & we all enjoyed it.