The ride itself is not very long, around two minutes. It's a smooth ride, not a lot of jerks or bumps like some other coasters. The ride is actually really good, the best part is not the coaster part, its the dwarfs part. You get to go through and see the dwarfs mining and the gems, maybe it was just because it was new, and I had never riden it, but I found myself acting like a little kid the first time I rode it, pointing and going "awww".
This is a great family ride, its not all that scary, tamer than Thunder Mountain and not as jerky Barnstormer. If you are looking for a thrill ride, you might be disappointed. But if you are looking for a mild ride, its really good. I would say that most kids would enjoy it and it would not really scare them. I would tell anyone with or without kids to make sure that they rode this ride. However if you can't get a fastpass you might want to wait until right before the park closes to see if the line thins out or hit it when the park opens.
Just to kinda give you a taste of the ride I have added a video of the ride so you can see what it's like.