I would also recommend Square, but if you are just standing it up for a one off, one day event, and it's the 2nd day of a two day conference and most folks may have already made their purchases on day 1.. might not be worth the time and effort.
You could probably get by with having a PayPal, Zelle, and Venmo account available for transfers because if someone doesn't have cash on them, they will generally at least have a PayPal account (and probably Zelle and Venmo, depending on their age). Not the greatest customer experience but it might be good enough. Venmo has a QR code that you should just have constantly displayed on a device so people can quickly scan it and make their payment. Not sure about the others.
Using a personal account is also not ideal in terms of maintaining supervision and control over the sales proceeds, but if RHB will know exactly how much should be paid to them based on what was sold, then that is a good mitigating control.