Went last August with my wife, 16 year old son and his best friend and we loved it! Great stuff from FWD, here is what I got.
National Museum of Anthropology is world class and worth every minute you spend in there. Plan for several hours to see as much as you can because it is vast.
Palacio de Bellas Artes is beautiful and we were lucky enough to visit during a Picasso and Matisse exhibit where there were hundreds of their works on display.
The Castillo de Chapultepec is worth a visit. The architecture and views are awesome. The artwork and other pieces are beautiful as well.
The pyramids and grounds at Teotihuacan are awe inspiring. About an hour car ride, maybe 45 minutes from the historic center of Mexico City. We used Uber to get there. Very affordable.
The Metropolitan Cathedral is beautiful and right next to the Zocalo and the Presidential Palace (which is ok, not great). I'm not Catholic, but I felt like one when I was there. Very powerful place.
For trinkets and souvenirs we loved the La Ciudadela Market. Prices and people were very nice. Clean, no yelling, and tons of stuff.
We used Uber for everything. Fast, friends and very affordable.
That's all I got for now, if I think of anything else I will add it.