Well.. that spare tire is something I'd really be concerned about.. whether you're going to jam in a full sized tire or try to get a spare. A scissor jack at minimum and a tire patch kit (or slime even) with an air compressor.
Otherwise.. advil for a sore back, sunglasses for the glare, and have fun
I only complain because I often do a big spurt of driving in a day to get to my relatives.. it's about 620 miles. I'd hope you break up your driving into a few days each direction to have fun.
The rest of the packing is really food and clothing wise
Oh.. keep in mind, BMW also has free road side service for the first few years (which your car will certainly cover). Usually this means 24hr tow to the nearest dealer to your location. Still.. AAA is kind of nice. With COVID at least in MA you cannot ride in the cab with the tow driver, so that forces you to call a cab. So in that case it might not hurt to setup an uber account on your phone ahead of time.