I could be wrong, but I think for the OP and this situation this isn't about training the dog to accept other animals around him while food is present. Normally I don't tout a behavior management arrangement as the solution to a problem. In this case behavior management will work (IMO) the best because the dog is to do its job out of sight of the owners most of the time. I will say though, that getting the dog OK with human presence near food might be a really excellent direction to go in, but I would not take the time to generalize that to every other animal the dog encounters. NO owner will be present to train, reinforce and correct every time. So why bother? If a good managment solution can be achieved then it will be a happy, well-working, team.
Feed the dogs seperate, no free feeding, and make it routine (which is training in itself).
Feed the dogs seperate, no free feeding, and make it routine (which is training in itself).