@Robbi1 Are there other Airbnbs in your area, hosts you might know, etc? If this happens every year for this event, it might be good to talk to other hosts around and co-ordinate responses. Like you could each have a list, with the URLs of each other's accomodations, then when you all get these requests, answer saying that the whole team and their friends can't be accommodated, but that there are also these other places they can split the group between, and also make clear that only the guests registered on the booking may enter the property, that unauthorized and unpaid-for guests will be denied entry or asked to leave. And mention some public places around where the whole group could get together outside the housing accommodation- parks, community centers, restaurants or bars, etc.
Or, you could do as I often have, and I know other hosts sometimes do when it's a big drunk-up party week, like spring break and they're in an area that get lots of young folk looking to party- just block the dates on your calendar for those days so no one can book. Better to not have any revenue for those days than an unwelcome or disrespectful group. And while you say this group left the place in good nick, assuming that they can have 30 people in and out, when they booked for 10, is disrespectful, or at best, clueless.