this would work on VRBO, I don't know about ABNB
-search your town as if you have totally flexible dates
-find houses like yours
-go to each house's "rates" tab and see what they're doing. Normal rates, summer rates, event weekend rates, etc
-look at each house's calendar to see whether or not they are booked on the event weekend
that should do it! might as well make a list and record minimum stays and cleaning fees and such while you're at it. good luck!