Wireless is OK..
But, being a wireless person... I would go for wired
.
First, reliability (70metres) is an issue here. And any kind of interference may compromise the reception (well, not likely in rural areas.. except in case of storms with lightning)
Second, there are some regulations about radiated power in certain bands (and using directional antennas means stronger EM field in certain places.. Of course, all is OK if nobody complains, and in Austalia nobody cares about this.. but still..)
The lighting issue can be taken care of by optical insulators (opto-couplers).
And how about power? If you are using 240V, then optical insulation may be pretty academic.. and lightning could do a damage even if local power (solar) is used, if there is no proper lightning rod installed.
When I will be building my observatory, I will use optical fibres for communication (not sure how available this is to the rest of you guys, though.. but for me the whole system is already in my drawer here at work
)