supervisor just texted me “Just a heads up, if we get Amazon Wednesday after/night, the CCA/RCAs are going to have to work running parcels this Thursday thanksgiving. You'd be finished by 2 or earlier, will let you know for sure”

Wednesday night i will be driving 4 hours away to go to thanksgiving with family, im not risking my sanity and mental health to stay here for this job, last holiday they called me in i was doing 4 routes by myself, im brand now only a little over a month in, I filled my truck and was out from 9am-4pm and i only took about 80ish parcels. I only know 2 routes and they want me to take for 4 i was going from one end of town right back to where i just was because i have no clue how to separate them and run them effectively, there’s no way i would be out by “2 or earlier” last time they gave me a problem because i left at 4 and didn’t do enough. I will be in friday struggling with all the parcels so genuinely i dont care that the regulars will have to struggle, they leave and get back before me anyway im always the one out in the dark. So how do i tell him im not doing this? I don’t even care if thats the main thing i was hired for