I completely ignore the activation action for magic ammunition. You are already spending an action to fire it, and burning money before finding out if it hits, and then there is usually a save after that.

The idea that familiars cant activate items is so arbitrary, I let them use the alchemist's elixirs for them since that's arguably the primary reason an alchemist would create a familiar in the first place. And fuck it, i'll let them reload a crossbow too, why not.