If by "cunning" you mean "so stupid it might just kill everyone in the party work", then have the fastest character stand in line of sight of the orcs, in broad daylight, and yell "Catch me if you can!".

The orcs are armored, therefore slower, and won't be able to catch up with your fastest character.
The orcs are also dumb, unwise and ugly, it wouldn't be too unlikely that they'd ALL go after the bait, leaving the entrance open, and making an opening so that the rest can sneak in. Once in and hidden the bait will have shaked the orcs, which then return back to duty thinking nothing of it.

On the other hand, the bait might die. And you'd be unable to flee from whereever it is you're trying to sneak into in case things go wrong.