Guess I'm a little late to this discussion, but I strongly suggest you do one thing at a time...barrel first to get what you want, then rack out and add vanilla, then keg or bottle. One bean split open is probably sufficient. You can always add more, but you can't take it out if you over-do it. As erockrph noted, it only takes a few days for vanilla to come through. Too much for too long (like, in a barrel) and it's too late to fix.