How often are you calling this river?

[GoCubsGo]

MP3 is 70/9/1.6 Button is 18/4.5/1.5

Party Poker No-Limit Hold'em, $ BB (9 handed) FTR converter on zerodivide.cx

MP3 ($109)
CO ($112.75)
Button ($98.50)
SB ($99.25)
BB ($102.50)
UTG ($66.25)
Hero ($195.50)
MP1 ($50.10)
MP2 ($41.20)

Preflop: Hero is UTG+1 with 8[img]/images/graemlins/heart.gif[/img], 8[img]/images/graemlins/diamond.gif[/img]. SB posts a blind of $0.50.
<font color="#666666">1 fold</font>, Hero calls $1, <font color="#666666">2 folds</font>, MP3 calls $1, CO calls $1, <font color="#CC3333">Button raises to $7</font>, <font color="#666666">2 folds</font>, Hero calls $6, MP3 calls $6, CO folds.

Flop: ($23.50) K[img]/images/graemlins/diamond.gif[/img], 8[img]/images/graemlins/spade.gif[/img], 6[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets $10</font>, MP3 calls $10, Button calls $10.

Turn: ($53.50) 7[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets $25</font>, <font color="#CC3333">MP3 raises to $50</font>, Button calls $50, Hero calls $25.

River: ($203.50) A[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(3 players)</font>
Hero checks, MP3 calls $42 (All-In), Button calls $31.50 (All-In), Hero?.

Final Pot: $319

I am confident that I'm ahead of button's AK. I called MP3's minraise on the turn hoping to hit my FH because I was pretty sure he had a flush or straight. But now I have really good odds to call this river after button calls MP3's push. Since he is such a fish, he could be overplaying top pair or 2 pair. But then again, button could be slowplaying KK or hit his set of AA on the river. Do you call or fold?