Wear gloves, use long handled tools, and take your time. Agave spines can cause pain but they can also cause a pretty annoying irritation (inflammatory reaction) afterwards. You might try to lift up the leaves and work around the edges beneath them. The more you can work from underneath, the fewer spines will be pointed in your direction. You might want to hack one or more of them back (ie. cut off all the leaves in your way) in order to safely get at the others, ie. make a sacrifice to improve your access to the pups you're trying to remove.
You don't need to get any roots to speak of. These plants will re-root quickly and easily. So you might try to use a pointy ended shovel and work around the edges, just hack off most of the roots, and pop the desired offsets up from underneath.