I always tried to give mine the good weapons and keep them alive because their unlimited ammo came in handy, but it was usually like herding cats. I found the best way to use the Marines was to give them rocket launchers and/or fuel rods guns and carefully shuttle them around to positions where they wouldn't blow us up trying to hit enemies that were way too close. Wish there had been a way to tell the kids to stay in the 'hog while Papa Chief goes inside to clear out the objective on foot.