House Rule - Critical Hits for Minions

So, last night, we had a fun encounter with numerous goblin minions backed up by a Tiefling Commander and a Goblin Skullcleaver. It was a large fight, with the goblins desperately trying to defend the inn they had been holed up in.

A very cool fight, with three different floors of combat, and each character involved in his own little challenge. The Eladrin Warlord and the Drow Rogue were trying to take down the Skull Cleaver on the upper floor. The Elven Ranger and an NPC ally named Arielle (A Human Warmage) were focused on a fight with the Tiefling on the roof, with the ranger occasionally firing down through the skylight onto the first floor (the first floor having a railing that overlooked the dining area). And the minotaur fighter trying to stop the little goblins from swarming him.

The problem? Minions don't deal any extra damage on a critical. And I rolled quite a few.

I personally think minions should deal double damage on a critical hit. And my players agreed with me on the spot, even though it meant quite a bit more damage to themselves.

Here's my logic: on a critical hit, the monster or PC does full damage. This can be a huge effect, especially when you factor in bonus magic item damage from a critical hit. In the first round, our ranger inflicted something like 40 damage on critical!

A minion's damage is a flat number. This number represents the average damage that minion would do, if he had been rolling dice. that 4 points of damage the minion does is really the average of 1d6+1, rounded down.

Now, if that minion got a critical, wouldn't it stand to reason that the damage he would inflcit would be a maximum, instead of an average?

So, double minion critical hits. Makes sense to me, and it's a new house rule.