So my parents spend their summers around Bozeman, MT and have many visitors while they're there (including me, the main biker in the family). The house is up a pretty long gravel/dirt road and driveway on the side of a mountain/large hill. They currently have a couple basic mountain bikes, but I've been put in charge of getting a bike more suited for road riding. I was thinking a cyclocross bike would fit the bill well, since realistically it'll get ridden more if people feel comfortable leaving directly from the house and going down the hill on the gravel/dirt road, but I might get an extra pair of road tires for those motivated to drive out to go on a true road ride. Here's the issue. I'm the tallest person in the family at 5' 8", but we'd like to get something that a taller visitor could also conceivably ride after making only minor adjustments (i.e., the saddle height). We're not looking to break the bank here and I don't imagine anyone will be doing any real aggressive trail riding with it (they'd use the MTB for that), so maybe a cyclo bike isn't necessary at all. Any general suggestions or specific suggestions for a bike that might have more flexibility re sizing?