miss it). It's always best in the early evening as it's in the shade. No fun when it's in the direct sun. But Sand Dune Arch sees sun for less than an hour a day. It used to be the best kept secret in Arches for people with kids. But the secret is out so expect it to be busy.
Obviously Delicate Arch is the highlight of any trip to Arches, but unless you and the misses are hearty souls who don't mind carrying young kids up big hills, I doubt kids that age (under 5-6) will make it.
Also, unless you've spent a lot of time at the Grand Canyon, Dead Horse Point is amazing, especially if you are leaving town that way anyhow. It'll add about 1 -1 1/2 hours to your ride home.