My wife is a photographer, and pricing for a family would be $500+. A 15 minute session wouldn't be long enough for family photos, IMO…especially if you have kids. Many are strict about the 15 minutes, so wrestling everyone will take time.
As far as photos, most packages come with a set number of photos and the ability to buy more. Some will be nice and throw in a couple extra, but I wouldn't count on it. Many also post the entire gallery for you to view and choose the ones you want (will be watermarked).
You have to remember, this is their job. You're paying for their expertise vs some mom with a DSLR camera from Beat Buy.