Is it possible to buy tickets for the slide/cablecar of Mutianyu at the top?

You can buy the tickets for the slide and cable car at the top. The operating time of the two facilities is as same as that of the Wall. After a tired hiking, most visitors may choose to go downhill either by slide or cable way. There might be a long line-up, you'd better get there early. Generally, a large number of visitors drive to the scenic area, so there should not be a lot of people waiting for the bus or taxi. But to make sure you have a nice trip, you'd better avoid to go there on weekends.