How do I know of Whey Protein is right for me?

Ive been reading up on whey protein and the benefits of it and would like to try it, however I'm not sure if my workout is intense enough. I usually do 2.25 miles of interval cardio (power walking/running/jogging) five days a week, sometimes six, on an empty stomach in the morning. I'm planning on increasing it to 3 miles this summer. Occasionally I'll do an ab workout 3-4 times a week max and squats/upper body stretches every night. I'm looking to continue burning fat but also built more lean muscle for a more fit and defined physique but not too buff since I'm a girl so is whey protein right for me and if so how much should I take and when? From what I've read I'm thinking after my cardio session and maybe at night but since whey is calorie dense should I take in the form of a shake for breakfast and nothing else for that meal? One last thin is that my mother and my sister also do cardio but not as many miles however they go for about 30min or so, can they take it as well? They're kind of on the heavy side but not too heavy and would like to burn fat.. Would this help them?