While I think $35-$45 is way too low, I also think one roll of film is too little. You're essentially shooting on spec, and if I were doing that I'd want at least two rolls per sitter. Close-ups, medium range, different angles, different settings or lighting. It gets worse if you are shooting a family of kids, because you need at least one shot where they all look good, as well as individual shots.
Originally Posted by Ektagraphic
You also have to consider that some people won't pay anything for a sitting fee unless you are very established with a great set of sample prints and referrals.
First, I'd figure out what market you're aiming at, and then set up your pricing to appeal to that market. If your aim is to sell prints, then set up your operation so the sitting is free, you take a lot of great pictures, and the prints make your money.
It sounds like you might be a beginner at this? If so, can I suggest doing some free sittings, and offering the prints at cost, for the first few times. Keep the right to use the prints for your own marketing, of course. You will find out if you are cut out for it. Also, you will, if you pick the right folks, find that they will promote your good work themselves, by showing your work to their friends.