Half the Dauni (and the ones we most want) are champing at the bit to come under our hegemony voluntarily. That, plus the League, the Peuketti, the Messapii, and Eretria itself, would make for a damn formidable target for the rump Dauni to try and take on.
We've previously granted slaves/funds to our lower-class citizens in lieu of trying to turn everyone into hoplites, and it worked quite well in spurring our commercial and maritime growth. Remember, we've got a thriving luxury sea-silk trade, and fishing is a major and respected industry for our citizens - Eusebios came from there, after all.