IMO at a company party, people are there for a good time
adding serious competition is not what most will go for
I would do a raffle that has nothing to do with the bowling
if you do have some that want competition, put them on a pair and do a one game winner gets (x)
also, the casual bowler is usually done after the second game
don't look at this from a serious bowler's perspective, give the group that they want, not what you want
hope it goes well and everyone has fun