What would you do? #170 - Baby flush facing paired board shove on river

Bodog $0.10/$0.25 No Limit Hold'em - 8 players
The Official DeucesCracked.com Hand History Converter

SB: $22.68
BB: $22.00
Hero (UTG): $25.00
UTG+1: $29.80
MP1: $16.50
MP2: $10.60
CO: $24.40
BTN: $28.86 - 65/23 / 25% steal / 0% 3bet / 0.7 AF

Pre Flop: ($0.35) Hero is UTG with 6c 7c
Hero calls $0.25, 1 fold, MP1 raises to $0.75, 1 fold, CO calls $0.75, BTN calls $0.75, 1 fold, BB calls $0.50, Hero calls $0.50

Flop: ($3.85) 2c Ah Ac (5 players)
BB checks, Hero checks, MP1 bets $0.75, CO raises to $1.50, BTN calls $1.50, BB folds, Hero calls $1.50, MP1 calls $0.75
Doubtful that someone flopped quads / boat, but this is definitely a scary board to chase.  Given the amount of callers, though, I think I'm priced in to chase.

Turn: ($9.85) Jc (4 players)
Hero checks, MP1 checks, CO bets $1.50, BTN calls $1.50, Hero calls $1.50, MP1 folds
???  $1.50 into $10?

River: ($14.35) 9d (3 players)
Hero checks, CO checks, BTN bets $25.11 all in, Hero ???
Huge problem; this is why I was afraid to chase on the flop.

Hero calls $21.25 all in, CO folds
Obviously, these are players that are level 1 thinkers; i.e. I have trip Aces... no one can beat me, given the show down.  I'm pretty sure this was not a bluff, but a "value bet."

Regardless, this is exactly my thought and why I made the call: there are simply a TON of hands that I beat that are making exactly this same move on the river.  I thought about this play; this kind of hand is so typical of the play I see on Bodog...  Wait until I'm behind to shove the river and hopefully force a fold.

Final Pot: $56.85
Hero shows 6c 7c
BTN shows Ad Th
Hero wins $54.05
(Rake: $2.80)