I would handle it totally differently. Rather than bring them some of your beer to show what you can do, go volunteer to clean out the mash tun, mop floors, clean kegs. Ask for a part time job helping the brewers (don't expect much money). Compliment the head brewer on his/her beers. Ask a few questions on what they do during the process to get their beer right. You might mention you are a homebrewer, but don't make a show of trying to get them you beer at first. Then, after you have gotten to know the group a bit ask if they would mind sampling your beer.
Remember that there's already a head brewer there that will be pretty proud (hopefully) of his or her beers, as will most other folks around him. So you don't want to come off "cocky" like you think you are going to walk in and blow them away with your beer. Get to know the people, and especially the brewer(s), and then they will be much more likely to give you both honest feedback and, perhaps, a chance to showcase your skills.
Now, that said, if the brewery is totally or mostly incompetent you might handle it a different way. But you might also be getting in way over your head. While the brewing process is essentially the same the tools pro-brewers use, the sanitation methods and the volumes they handle are quite different. If they have problems with their beer there is a good chance they are just going to turn around and brew your recipe with the same flaws in tact.