@Tim789
You absolutely shouldn't be asking your guests to cancel. You are doing them an enormous dis-service.
Although you are an experienced host with over 100 bookings, it sounds like you haven't familiarised yourself with the basics around how Airbnb works.
You can ask Airbnb to cancel the bookings under their Exceptional Circumstances policy (see Airbnb Help Centre).
They will offer the guests a complete refund, 10% credit to help them find somewhere else and help in finding alternative listings.
Call Airbnb now and stop asking your guests to cancel.