What happens if your flight is delayed for some reason and the delay puts you outside your 72 or 120 hour testing window? Are you hosed?

We leave on 6/1(Tuesday) which is the day after Memorial day. I'm trying to time everything so that we have our results in time to submit them to EHAS, get approval, and have our bases covered before making the 3 hour drive to MCI airport. Our testing place told me today that the PCR tests take 3-5 days for results. The Antigen test yields results in 30 minutes. I'm thinking about getting the Antigen test on the Saturday before we travel. Once we have the results, I would complete the EHAS form and hope and pray we receive approval by Sunday. But then I started wondering what would happen if our flight should be delayed? We could wait until Sunday to get tested to give us more wiggle room, but then we have to worry about getting approval from EHAS in time before we leave. We will probably drive down to KC Monday night and do a park and fly, so would like to have everything done by Monday morning or early afternoon. Would appreciate insight and thoughts about the best strategy to cover all bases so we have a good plan going in.

TIA