Venue Agreement - Standard Cancellation Policy?

I would at least get it in writing (through an email, etc) stating what happens if they cancel (will they give you a full refund?, can they find you another place for your wedding?, etc). In my photographer's contract, she stated that if they canceled for some reason, they would make sure they found a suitable replacement for my wedding. My ceremony musicians didn't have anything in their contract that said what would happen if they had to cancel so we just told them what was included in my photographer's contract, and they agreed to uphold the same thing. If you have something in writing, you have something to back you up if something were to happen (and you know the expectations before you sign anything).

If I ask them to add it to the Agreement, what am I asking them for? I'm not sure what's standard. Do I ask for assistance securing a backup venue? Do I just ask for money back? If we want it updated, I think it's best to have an idea of what we expect or would be comfortable with.

You should ask for both. Assistance in securing another venue (maybe they have other places they are affiliated with), and ask for your money back, including the deposit. If they cancel on you, you're not going to have an easy time finding another venue, as venues often book a year or more in advance. So, you should be entitled to a full refund if they do that.

Unfortunately, I'm not sure asking for that will work. The venue is a local brewery, there's no second location, and they don't require a deposit, just payment in full prior to the event.