scare card on the turn

[DjSkyy]

I have a question about a NLH hand i recently played online. Either the people involved had sat down recently or i hadnt been paying attention because i didnt have any specific information on either of their playing styles, and therefore assumed they were typical players during the hand.

Preflop: i was chip leader (approx $820) for the game and limped ($2) from early position with 4c 4d, three others limped behind me, the sb raised to $10, and i along with 2 of the other limpers called.

Flop: It came down 2h 4s 8s. The sb bet $39, and i briefly considered slowplaying because the guy to my left had a decent stack, as did the small blind, but i decided with that board i should play it fast and try to get heads up all in right away with the small blind who hopefully held an overpair. So i raised to $80, and the guy to my left immediately called, as did the small blind.

Turn: The turn brought a nasty looking 9s, the sb checked to me. They each had about $150 left in their stacks and the pot was now about $280. What should i do???

The way they both called a big bet on the flop made me think there was a good chance the spade on the turn completed a flush for one of them, but with a big pot like this i figured i was getting approx 3:1 from the pot to play against one of them for $150 more, and the chance that i was either ahead now or could fill up on the river seemed to indicate that i should move all in. I realize that i was not terribly likely to get a call from a worse hand or a fold from a better hand, so perhaps i should check and try to induce a bluff from that last player, but then i thought that since i was going to play anyway it seemed like i should set them all in now in case it should get checked around and one of them held a lone spade and the 4th one was to come on the river.
Any thoughts or suggestions would be appreciated