What would you do? #56 - Facing checked river on a straight possible board

From the full ring tables... (Both total lags VPIP > 55)

Full Tilt Poker $0.25/$0.50 No Limit Hold'em - 8 players
The Official DeucesCracked.com Hand History Converter

Hero (UTG+1): $58.50
MP1: $50.00
MP2: $25.50
CO: $52.00
BTN: $55.60
SB: $51.80
BB: $50.00
UTG: $86.10

Pre Flop: ($0.75) Hero is UTG+1 with 9h 9c
UTG calls $0.50, Hero raises to $2.25, 4 folds, SB calls $2, 1 fold, UTG calls $1.75
I don't want to see an UTG limp inviting everyone and their brother to call along with. Therefore, I raise to isolate. This player has proven to be a donkey who will limp / call -> fold frequently. SB comes along, who is the other donkey at the table.

Flop: ($7.25) 7h 9d Kd (3 players)
SB bets $0.50, UTG raises to $1.50, Hero raises to $6, SB calls $5.50, UTG calls $4.50
Middle set. Bingo! And action! With the 2 diamonds, though, someone is surely on a draw. I am going to make them pay for their draw. I was afraid of betting full pot here where I'd lose the customers, so I opt to bet 3/4 pot. I'm actually surprised to see them both come along for the ride.

Turn: ($25.25) Js (3 players)
SB checks, UTG checks, Hero bets $20, SB calls $20, UTG calls $20
The Jack completes the QT straight. They both check to me. I really really want to discourage a Q from calling here, because there's a lot of scary river cards that can fall. I'm very afraid of the straight, but since they both checked, I don't want to give up any free cards at this point if they don't have the straight.

River: ($85.25) 5h (3 players)
SB checks, UTG checks, Hero bets $30.25 all in, SB calls $23.55 all in, UTG folds
Another "thin" bet, where perhaps only a better hand is calling here. Given the way he played the hand, though, is he showing up with QT?

Final Pot: $132.35
Hero shows 9h 9c (three of a kind, Nines)
SB mucks Ks 3h - Are you kidding? K3o is hard to lay down both pre flop and beyond... ESPECIALLY given the action... Thanks for the stack, donk.
Hero wins $129.35
(Rake: $3.00)

The what would you do is: Are you betting the turn and river? If not, why not? I think you're missing HUGE value by checking down, and I'm discovering that against donkeys like this, far more times than not, you're going to actually get a call from worse hands.