@lje62 - I am sure they are all good kids, but if you want to make sure it is an alcohol free party then walk around your property, especially near the garage apartment to make sure there is no alcohol stashed. I would also go check up on them few times during the night and make sure everyone is accounted for.
My kids are 22 and 26 now. They are good girls, but when they were in high school I knew too many alcohol free parties turned into “why there were so many beer bottles” (or other liquor bottles) at my house the day after. I much preferred my kids to go to parties where there were alcohol and parents were aware, so they could watch out for any abuse.