As long as you don't sell to general public, you probably won't have to have the beef USDA inspected at processors.
Now...
Two ways you could charge your family for the beef:
1) The actual cost of the animal, its care & feeding, etc., for the time you have owned the animal, plus the processing costs, and your travel expense to and from the processors, would be your bottomline break even cost for the animal (live weight), DIVIDED by the number of POUNDS of packaged beef you ended up with.
2) The average SALE price for an animal at an auction in the weight class for your breed, divided by the number of pounds of processed/packaged beef you end up with.
Either method will give you +/- a break even cost for your animal.
Or, you could sell your family "shares" of the animal (quarter, half of beef) and let them pay the processor. Share price would be based on either #1 or #2 above.
Note: Obviously, hamburger is worth less than prime rib (yours or the supermarkets). To keep your family members from killing each other on the deal, you would probably need to prorate the packaged costs based on # of pounds of each cut they got, etc.