I presume we are talking about someone stood on the dais in the High Street next to the Mayor/Chairman of the Parish Council/Dave from Tesco's as the massed ranks of space cadets, scouts and brownies troop past.
IMHO it should be the senior commissioned rank present and s/he should outrank the bod marching the troops past, ordering the 'eyes right'.
If the only military bod handy is an NCO, s/he would not respond to a salute other than to stand smartly to attention, so leave the response to the eyes right to the senior civilian dignitary (the aforementioned Mayor/Chairman of the Parish Council/Dave from Tesco's) who should doff cap, bow head, give big thumbs up, whatever the local custom might be.
Better still, get the local Legion/RAFA branch to get one of their senior blokes in beret and blazer to throw one up as you glide past in full sail.