We got to Monument Valley midday in spring (April) and unsure of what we were going to do there since COVID forced the closure of the Tribal Park. The kids spotted a sign for D/D MTA and forced us to call. To their (our?) delight, Sheila answered the phone and was able to book us for a tour later the same day.
Guy and his family were kind, patient with us and our 3 kids, informative, and entertaining. The tour was fairly priced and the horses were gentle and easgoing even after a long day. It ended up being a perfect way to see the sunset and experience Monument Valley. Definitely would recommend for families with children of the same ages (5-10). It was one of the highlights of our entire trip in UT and AZ.