There is a limit of 50,000 on a credit card transaction.  If you have established an account that has done this frequently in the past you should have no problem, I swipe 3,000-5,000 transactions once in a while tough usually $250 average.  If you have a newer account simply based on feedback I have seen here and elsewhere I would think that there will be some monitoring of your account and more checks into your business with funds held during that time, though I don't believe there are any specific statements on how it will be handled.

My best advice would be to call in today and talk with a Square representative and make them aware of your event and see what they have to say.  contact Square