How to play nuts Vs. Freeroll

I find myself coming to this situation often.
Take this hand for example.
Im holding 5 [img]/images/graemlins/diamond.gif[/img]6 [img]/images/graemlins/diamond.gif[/img]A [img]/images/graemlins/spade.gif[/img]K [img]/images/graemlins/club.gif[/img] There are 4 limpers.
the board comes
2 [img]/images/graemlins/heart.gif[/img]3 [img]/images/graemlins/heart.gif[/img]4 [img]/images/graemlins/club.gif[/img]
So im first to act, and of course i bet the pot.
Villan reraises. Everyone else folds. (Villan is tight and from the previous reads i have gathered from him, i am quite certain that he has 5/6 and a freeroll flush draw.

So do i just check call check call and hope no [img]/images/graemlins/heart.gif[/img] comes? or do i fold? I mean, the only thing im drawing to is a split pot and it would cost me dearly if he spiked a heart on the turn and even more so on the river.