I don't believe it was a ritual either, nor did the prosecution ever claim as much.
Well hypothetically, say you had all the proof you could ever imagine that the three committed the murders: one what grounds could you figure Echols' documented quest for power though drinking blood and such would not have played some role in motivating him to attack the boys? Particularly given Echols' belief "that the younger of the victims would be more innocent and in turn more power would be given the person doing the killing" as he agreed on the stand that he told Ridge?
First, you are asking me about my opinion so there's not going to be any proof to cite to or quote. IF it played out as you say, I simply don't think the impetus for killing the boys was because of a satanic/occult belief system whereby one gains power by drinking blood. I simply believe it would have been because of a deep seeded psychological issue. Now, that deep seeded psychological issue may have also led to him to making that statement under your scenario, so there could be an interplay between it all. I'm not sure if this will make sense, but I don't think he would have seen the boys and thought, well there is a good source of power if I can drink their blood.