Chad: C'mon man, call'em on it. Make a party out of it. Everybody shoots, someone buys the beer and dogs, someone cooks, everybody has a good time - but everybody shoots. If you have any non-magnum calibers that an inexperienced shooter could use and possibly hit at 300, it would be a super plus for you.
The last time I did that was years ago and it wasn't summertime. It was the dead of an upstate NY winter and it was bitter. I was developing a wildcat cartridge for my 1911 and shootin' silly-wets with it and none of my friends or co-workers could believe I was hittin' - and knockin'em down - at 200m with a 1911.
I made arrangements for additional shooters with the range monster, brought along spare ammo, coffee and hot dogs and those who came along had a great time. Even got myself a convert - that is I converted him from a non-believer to a believer.
Had a ball years ago with a couple of Browning P-35s with tangent sights. We were shootin' ball ammo at a large quarry pond in the middle of nowhere and elevating the sights to get our distances. You would be surprised at the elevation it takes to send a 9mm round from a short barrel out to 4-500m. We took some light colored balloons, inflated them and dropped them in the water and then went back a couple of hundred yards and tried to hit them. Those old Brownings were pretty accurate at longer ranges but we managed to pop only one balloon - hit a couple and skipped them a bit but popped only one.
Truth is buddy, ya can't take non-believer statements seriously especially when they are unwilling to witness something contrary. Ya have to consider the source. Whenever someone says 'bs' to me I always offer to show him or her that it is not 'bs'. I also tell them that if they do not wish to witness a demonstration that counters their statement and offers proof to the contrary I can understand their cowardly wimping and lack of manly willingness, and leave the offer open...............it usually works. JMTCW. Mikey.