Depends how it pans out, though. You could look at it two ways, I guess: Either the added difficulty (it's harder to avoid sheep the more managers there are) makes it more fun - or, well, the opposite. It gets too sheepy, and the sheepiness gets tedious.
Impossible to say for sure until we get going, though.
One thing I'm very unsure about it how wise it is to let the managers nominate sheep. It could be loads of 'em, and it could take forever - with the inevitable arguing about how sheepy the sheep should be.
I'd rather have the Evil Committe just hand out the sheep - I don't really see the upside to letting the managers have a say in it.
PS If it's a work load issue, just invite more neutrals to join the sheep committee.