For this many people, whole hams might be your best buy. The shank is easier to carve. If you are doing the country style, dry cure ham, you MUST do the multi day soak (I use milk made from nonfat dry milk), then simer, to get a really delicious result
Bone in, you need to look at 60 pounds per 100, so I would aim for at least 45 pounds.
General ham info. According to USDA standards, hams containing at least 20.5 percent protein and no added water may bear the label, "ham." With no less than 18.5 percent protein, no water, may be labeled "ham in natural juice." Such hams are usually sold on the bone and may be fully or partially cooked for your convenience. Hams containing up to 10 percent added water while maintaining at least 17 percent protein, are labeled as, "ham, water added." Many ready-to-serve spiral sliced hams fall into this category. Hams labeled as "ham and water product" can legally contain more water than ham and are usually boned, reconstituted and molded or tumbled into a ham-like shape.