It's the simplest set, to be sure. Like I said earlier, I'd prefer to have a single attack roll and roll deviation from center for each grenade. Of course, I'm looking for maximum saturation, here. It is, however, the slowest method.
Now that I've thought about it a bit more, just using the burst fire rules as-is would be the quickest solution (not necessarily the best). That way the burst fire can increase the damage and thus the explosive radius, or decrease their defense since you are spraying the area with high explosives. You can also move on more quickly to someone else.