Do I (or the ground crew) have anything to worry about ?
Short answer: No.
Slightly less short answer: The radar power levels in modern aircraft are pretty low. As far as we know, the only bad effect from radar exposure is the possibility of heat damage to tissue (volumes with poor blood supply, e.g. eyes are the first to be affected), which I suggest would require orders of magnitude more power than is produced normally. Even at 20ft away, you would only be intercepting a small fraction of the total beam energy and of that, another fraction would be absorbed rather than reflected/scattered.
It is still best practice to turn the things off and limit exposure, though.