It doesn't hurt to show friends a price list and then tell them you will give them a significant discount, because they are friends, swearing them to secrecy. That way they will appreciate your "value" more and when they refer business your way they won't say "he/she did our shoot for free". You can discount to the point it just covers your costs. Most good friends would at least want to cover your costs.
In exchange for the discount, ask them to sign model releases so that you can use the images for self promotion without any restrictions. You'll need to put together a good release and will likely need one for each person in the shots (any kid's release needs to be signed by a parent/guardian). It could just be the "core" of the family that's released, and you will only be able to use the images of them, not Grandma, Grandpa and Uncle Joe, if they are also in some shots.
If you need a release, Google up a copy of the ASMP release as a starting point. It's a good one.
Get in the habit of doing paperwork right away... Think about signing a contract with them.
You just need to license the images for their personal use in perpetuity, to include third party printing of the images on their behalf... non-transferable, no additional rights, no commercial usage without further written permission of the copyright holder, which you should spell out in writing that you retain.
Maybe next year they'll order Christmas cards from you using the images.