$50NL: 2nd pair + nut flush draw when I know villain flopped an ace

[O.T.G.]

Villain is a 50/0 player. After limp-calling and then donking into me on the flop, he has an ace probably 99% of the time. Since I probably had no fold equity was my line(call, call, check river) the only good option?

Full Tilt Poker No-Limit Hold'em, $0.50 BB (8 handed) Hand History converter Courtesy of PokerZion.com

UTG+1 ($87.80)
MP1 ($52.80)
MP2 ($31.60)
CO ($21.50)
Hero ($50)
SB ($42.80)
BB ($43.45)
UTG ($28.20)

Preflop: Hero is Button with K[img]/images/graemlins/spade.gif[/img], Q[img]/images/graemlins/spade.gif[/img].
<font color="#666666">3 folds</font>, MP2 calls $0.50, <font color="#666666">1 fold</font>, <font color="#CC3333">Hero raises to $2.25</font>, <font color="#666666">2 folds</font>, MP2 calls $1.75.

Flop: ($5.25) K[img]/images/graemlins/club.gif[/img], A[img]/images/graemlins/spade.gif[/img], 9[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">MP2 bets $5.25</font>, Hero calls $5.25.

Turn: ($15.75) T[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">MP2 bets $8.5</font>, Hero calls $8.50.

River: ($32.75) 7[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
MP2 checks, Hero checks.

Final Pot: $32.75