it will be the exact same proportion of white and dark meat as a whole bird. just less of it all.

general rule is to get about 1.25 lbs per person to account for bone and seconds/leftovers, so a 5 lb half (I assume it is bone in) would be about the same as a large rotisserie chicken. for some people that might be 2 servings, for others it could be 8 or more.

a 10 lb bird is pretty small as modern turkeys go but your half should give a good meal for 2 plus some leftovers for sandwiches or whatever. don't forget to make some soup with the carcass.