Homer makes a good point. Just what I was thinking. Timber gates, especially double one are always "moving". It'll depend on the weather, temperature etc.
You'll most likely get it set up nicely.......... then after a while, the latch and the keep will decide not to line up any more.
Be aware that you possibly won't be able to see the numbers in the dark as well.
All kinds of locks here .................
http://www.ironmonger...y/Code_Operated_Locks
........ including digital and biometric fingerprint ones.
More expensive, but less troublesome, would be electrically operated "arms" that fix to the top, or one side of the gates. They could be operated by a waterproof switch, or by a handheld remote control.