@Sam397 I would absolutely not just cancel from your end. The 'no penalties' to hosts currently only applies for the period stipulated in the COVID-19 extenuating circumstances policy, i.e. to mid April (and some hosts that do qualify reported that they got penalised anyway). As you are talking about guests in late April/early May, you are not covered by this and would be penalised as per normal, e.g. losing Superhost.
You need to get the guest to cancel, or Airbnb to do it on your behalf. Unfortunately, right now there is not much chance of that because Airbnb is TELLING guests to hang on to the booking and cancel last minute as they will be extending the COVID-19 policy beyond mid-April.
I have had exactly this same experience and the guests then don't understand why this is not a fair solution. I also offered additional refunds, but I guess they do not believe me either! One guest said that by keeping the booking and cancelling at the last minute, I as the host would 'lose nothing'. It's like they think the property lives in some fantasy land where the mortgage, bills and local taxes pay themselves while they sit empty.
I am not expecting Airbnb bookings in the next few months, but I would like to take in long-term renters if that is even an option in the now severely overcrowded rental market. However, I cannot do anything with my rooms held to hostage.
I would suggest you do what I am doing. Advertise your rooms elsewhere. If you know the guests have no intention of keeping the bookings, cover yourself by trying to get new renters in from another source. If, by some bizarre chance, a guest ends up keeping their booking, you can tell them, "Sorry, but you told me you were definitely going to cancel, so I had no option but to fill the rooms." If you have to face Airbnb penalties for this, then so be it, but don't expose yourself to them now by cancelling bookings that fall outside of COVID-19 EC.