Hi T.,
I love the idea of photos for parties. It really depends on where you live and the disposable income of the area. I am a professional photographer and know photography is one of the first items not considered essential. I am by no means trying to discourage you.
There are a variety of ways to do this, you can charge for just your time and a flat fee for the photos, download them on a cd for the family and give it to them, this would be the least expensive for them and you are done and not spending more time printing and putting albums together. That is the other option, where you charge for the prints, your time for photoshopping any of the photos, album.... If you have people that can afford this it is a wonderful service and a lot of fun for you. I would just make sure you are charging enough for the time you have invested, people don't realize how time consuming it is and assume after the photo is taken that is it.
A couple of other hints, make sure you have several memory cards, don't do an entire party on one card. There was a photographer a couple of years ago that took wedding photos, all the photos were on one 2gb card. Something was wrong with that card and he lost every photo, the family sued. Better to have several cards you switch out through out the party so if something happens to one you are covered with another card. Also make sure you make a cd or have a seperate storage other than just your computer for the photos, your computer crashes you want a back up. Don't delete your cards until you have another copy.
I wish you the best of luck,
have fun,
SarahMM