I'd agree with the US 285 route. Salida is a great overnight stop (you may decide to go no further than Salida, once you're there!).
I would avoid Pueblo SP in August -- the heat will be oppressive and the scenery just isn't that great.
As noted, there's little to recommend in the Telluride area. Matterhorn NFS CG south of town does have a few sites with FHU, but as you can imagine, those book up early. Stay in Ouray and take a day trip to Telluride. We've never stayed in either one (we prefer to stay near Silverton), but both the KOA and Ridgway SP seem to get a lot of recommendations here. The scenery in Telluride is great, but the town is something we just go past anymore. It used to be a quaint little town somewhat similar to Ouray, but we went through there 15 years ago or so and noted many of the great little shops had been replaced by real estate offices.
I don't know how old your kids are, but the hot springs pool in Ouray is worth an afternoon. Great pool with slide for the kids and amazing views for the adults. There's also Box Canyon Falls near town. A trip into Yankee Boy Basin is a great way to see amazing wildflower displays. If you don't have 4x4, rent a jeep to get you further up the road. In the San Juan's, the best wildflowers seem to be right at or just above Timberline by early August.
