Horsesareforever, don't worry about what others think, but its great to have this forum to make sure you are doing the right things. I love it! I have found over the years horse people are very opinionated! Every one has a different way of doing things. In my barn my friend and I were considered the "bad ones" because when we trail ride we would go for about 2-3 hours, we would walk, trot and sometimes let the horses gallop for 10 mins or so. (this was in fall and winter, not summer) and everyone at the barn thought we were nuts and did not want to ride with us.
I feel that the horses love to get out on the trail and blow off some steam. I think the people who don't ride their horses (the healthy ones) are really the ones that are hurting their horses. (they are bored just sitting in the pasture all day every day)
As for your work out sounds perfectly reasonable to me as long as the horse gets a day or two off now and then