If you have a problem, try this: attatch some sharp nails to the frame of your robot, sticking into the air (but not inside the bot), or hang a conductive fringe (metallized foil decoration) from it. This will allow the charge to dissipate without building up a large charge, which lowers the voltage = length of arc. Remember, for a robot of fixed capacitance, V varies as Q (Q=CV)
Don't have the points hanging down toward the HDPE, though, like the combs on a Wimshurst machine. That would only aid in transferring charge.
If they remain insulated, your crew can approach with a math protractor pointed at the robot (as they close from min 4 feet). Once they touch the point to the 'bot, they can pick the 'bot up, and point the protractor at the end-of-field diamond plate (as the approach and touch it.
This suggestion won't help the on-board electronics, but the points on the 'bot might.
I've played with Van de Graafs and Wimshursts; they can be a real pain. Maybe the venues are way too dry at this time of year.
Are your shoes synthetic-rubber-soled ?
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BTW, There is little difference in specie between ESD and lightning, only in magnitude of charge (them's cool ohms !) and voltage. The lightning storm just "builds" charge continuously, whereas our puny efforts with fur and bakelite have limits. If we had capacitors as big as the Earth / Cloud / Air dielectric thing, and enough time
!
And, in another vein, many of the accidents with electricity aren't because the heart has stopped, but because the sudden jolt gets a reaction - somebody jerks, or drops sometihing, or loses his grip. This would apply to many static shocks !