10 days are more than enough for these three places. Actually, Huanglong is very close to Jiuzhaigou, which can be counted as one place with Juzhaigou.
About the transportation between Jiuzhaigou and Zhangjiajie, you need to go to Chengdu to take a train or plane; plane is better, for there is no direct train from Chengdu to Zhangjiajie yet. Zhangjiajie scenic area is very big, you'd better hire a car for the consideration of the elder.
About the cost, it's really hard to say. It depends on what kind of hotels are you going to live and what transportation way are you going to use, etc. You may refer to this tour--- Side Trip to Fairy Jiuzhaigou(https://www.travelchinaguide.com/package/tour-cd05.htm) for the price; the hotel included are high level, which costs more.