@Jeremy722 While it's against Airbnb policy, it's really up to the discretion of the host (Airbnb actually tells hosts this if they inquire, but will also cancel a booking on request if the host realizes after it's confirmed that it's third party) and some hosts have taken 3rd party bookings without incident.
As new hosts, I would definitely not advise you to accept it, though. Not only will Airbnb not support you if something goes wrong, they can be very problematic if the guests haven't actually read the listing description and arrive with false expectations, the booking guest can write the review, which doesn't actually reflect their own experience, etc.
If you were more experienced hosts, if the booking guest had a good history with Airbnb , if they communicated really well with you, and if it wasn't just a weekend booking, which can mean party time, it might be different. Occasionally a guest might want to surprise their parents with an Airbnb stay for their anniversary, or something like that- while some hosts take a super hard line on third party bookings, others have accepted them on occasion. It really depends on the circumstances and whether a host is willing to take the risk, but in general, it should be a no.
And it certainly should be a turn away at the door, if the person who arrives isn't the person who booked, and that was never mentioned.