I don't think its right for your family to require you to do the work you do for a living for free unless they do the same thing. If your uncle was a mechanic, would he work on your car for free? If your aunt was an interior designer, would she do your house for free? If the answer is no, then you aren't in that sort of close relationship with them.
Personally I have family members who I wouldn't hesitate to help any way I can, anything and for no money, but I also know that in general unless they couldn't afford otherwise they wouldn't put me in that spot.
Personally I would go, DONT shoot 1000 images, shoot 300, minimal batch post processing, and give them a DVD with the images on it. Say clearly that this is a one time thing, and that you aren't willing to do it for anyone all of the time, since you aren't. Make sure they understand what the going rate for professional photography is - YOUR going rate. You charge X amount for a 5 hour party, and people hire you for that money, but this one time you're being nice enough to give it for free because they didn't understand and you didn't want to disappoint them.