Do high impedance pins have input capacitance?
Yes there will be output capacitance of a few pF. 

The 'typical' output capacitance is stated to be 5pF measured with a small test voltage near Vcc or 0V on the output. Because there are internal structures such as isolation and protection diodes that have a capacitance that varies with voltage there is not just one value, but you should be safe if you assume a maximum of maybe 10pF internal to the chip.