Travel recommendation please

Im coming to Morocco for the first time for a wedding in Marrakech. The wedding is Thursday-Sunday in December so we plan to arrive at the hotel on Wednesday. We are flying into Casablanca and land Monday morning, so there isn’t much time to travel elsewhere. At first I thought we could just stay in Casablanca / Rabat and spend a day each exploring those cities. The more I read about traveling through the country, the more I hear that those places are not super recommended. Then I thought maybe we can land, take the train to Tangier, and then take the midnight overnight train to Marrakech Tuesday night. Other people say visiting the south is ideal. It looks like we will have some time to explore Marrakech around the wedding festivities (there’s like one long event each day) and will have time Wednesday to explore so I don’t think we need to go there early. I know I messed up by planning my trip with so little time, it was just the cheapest flights I could get and the only direct option and it is not refundable

Can anyone help steer me in the right direction? Should we just do Casablanca / Rabat/ Meknes? Should we do tangier? Something else you might recommend?

I’ve read about how Fes/chefchaouen/the desert / Atlas Mountains /Essaouira are all awesome but don’t feel like I can make it to those.