No longer a newbie, moving up!
if you take that aproach that you will never make somthing then your right. If your in a business you should set yourself up like a business . Me personally i'd just go on an hourly rate, if your hourly rate is $100/hour then they have a two hour shoot coming to them regardless of the amount of family members. if it takes more time, then they are on the clock. I would talk with them. see what photos they want and then figure out roughly how much time that is going to take me and then explain my pricing, how much time they were getting and what I estimated the time to be. so they know they have 2 hours for free. they know they have to pay after that two hours so if things strat dragging on they may go "okay we need to get this done so we arn't paying out of pocket". or they may not care and just decide to do more and you wind up taking home some money. it also leaves you the option of going into that third hour and telling them youve had such a wonderful time with them that your not going to charge them for that extra hour. they go home thinking how wonderful you are to work with and you possibly get repeat work because of how you were so willing to work with them.