If they are starting their drive Sunday, they probably won’t be in Orlando until Monday night or Tuesday, correct? I don’t think they will have any issues. Florida is working hard to make sure there is fuel trucked in now, as close to the storm as possible. 95 should not have the same issues that 75 had yesterday with evacuation traffic and lower fuel levels at gas stations, since 95 is on the opposite side of the state. Outside of Florida, fuel supplies are normal. The hardest hit areas will have sporadic fuel shortages due to people using gas in generators, so it’s a good idea to fill your car prior to reaching those locations.
If they decide to make the trip, they should be fine through Jacksonville. Beyond that, I would just recommend making smaller but more frequent fuel stops (maybe top off at a half tank instead of waiting for a quarter tank) during the rest of the drive to Orlando. That is what I did driving up 75 yesterday and I did not come across any station that was out of fuel, even passing through where Helene devastated Florida and Georgia recently. The goal should be to arrive in Orlando with their tank as full as possible so they won’t have to worry about fueling up on arrival.