As long as your boss doesn't mind, I think it's a great idea! The more bonding time, the more of a chance Castiel has to get used to you. Also, bring a travel cage along and a water bottle and treats, just incase they get restless!
I wish I could bring my babies to work, ideally I was going to be able to. But I'm too much of a chicken to ask my boss, I've since realized that gliders are illegal in PA (I live in Jersey, but work in PA), and I couldn't really conceal it because mine are very noisy sleepers! LOL