IMHO your snakes are definietly being fed too much. Snakes will move for other reasons than hunting for food, which shouldn't be confused with that (Hognoses are especially active little snakes). They will also come out when they smell food. Snakes in the wild often have to take what they can get, when they can get it, so they will eat way more than they need to to stay healthy in captivity if allowed. While some snakes may eat more than others, it is unlikely that all yours need to be fed that much.
At 3', your boa should definitely be on to larger prey items that mice. Medium rats would be more ideal. Most adult boas and pythons (mid-sized) only require a meal once or twice a month. While each snake is unique in its need, I think a general guideline for you would be weekly for your younger snakes and bi-monthly for your older animals to be safe