Our caterer suggested 1.5lb ice/person... to account for use in water, soda,
mixed drinks and shaken cocktails (we limited it to 5 vodka-based martinis).
This turned out to be more than we needed, but many people were drinking wine
and refrigerated beer with dinner. Perhaps 1lb/person? That would make 6-7
10lb bags, though considering how cheap ice is, I might go safe and estimate
high.