Um, given that al Shabaab called in the press to parade these recent graduates from "basic training", so the exercise wasn't exactly top secret, don't you think we could have spared a Predator or two?
And given that they are all wearing their standard issue military sandals, if the cost of launching Predator missiles is prohibitive why don't we just go with a low tech solution and just drop large quantities of tacks?
http://mypetjawa.mu.nu/archives/206388.php