Photographers: how do you get everyone in a group shot (4-10 people) in focus when shooting manual?

Yes, use a smaller aperture to increase the depth of field. To compensate your exposure you can slow the shutter speed, increase the sensitivity and/or use flash and lights. Being a prime doesn't mean it's mostly used for close-ups. 50mm primes used to be a general walking around lens on film cameras and was the lens most commonly included as the "kit" lens when purchasing a camera, so was thought of as the most general purpose lens around. On a crop sensor body you narrow it's field of view so reducing it's general purpose usefulness but you should use it for everything you feel comfortable with. The group shot simply means you'll have to stand slightly further away from the group with the 50mm, it's worth using the 50mm as it's the better lens out of your two lenses by miles.