Could the cops do anything?

I’m having a party at my house tomorrow night. I’m 20 years old, but there will definitely be alcohol. Several (specifically four) of my 21+ friends are buying booze and bringing it over. If someone snitches and the five-ohs show up can they card everyone who will be here to see if they are 21 or older? Or can we just show the IDs of the legit 21-and-overs who legally bought the alcohol and be ok?