@Laura5333. First step I would think is to get the insurance assessor out asap so you know the full extent of the damage and the likely timeframe for repairs (so whether all future bookings are affected or just some). Be conservative with trades availability.
Then you can start to contact guests- depending on their plans they may be happy to defer or yes, get a full refund. Once you know you can contact Airbnb support if you just want to give full refunds, but I think there is value in contacting guests personally so they understand why and are more likely to re book later once you sort it out (goodwill).
Also ask Airbnb to provide assistance to guests with alternate accommodation.