I'm having my family over to Hanukkah dinner and want to prepare a standing rib roast. We are 6 adults with smallish appetites and 3 young children 9,7,6.Of course there will be the traditional fixings along with the roast.Last year the butcher advised me incorrectly. Now I decided to go to those are in the know. Those of us on Chowhound.How many ribs do I actually need and what should the roast weigh? Thanks in advance.