Possibly the stupidest idea ever...

How about this...
Have the aircraft depart and orbit an easily recognizable ground
reference about a mile or two from the gravesite. Use altitude
separation to deconflict aircraft according to speed (fastest higher to
slowest low). Brief for the overflight altitude to fly when inbound to
the gravesite.
Someone on the ground with a handheld can call them in at the
appropriate time.
Number the aircraft 1 through n. After they have been told to come in,
as 1 passes over the ground reference, he/she reports "One's inbound."
Two goes next and repeats the procedure, etc., etc.
Have all the aircraft fly in trail, fastest to slowest.
As they pass over the gravesite, they dip a wing in salute, and continue
straight on out for five miles.