#1 I don't think the Japanese visiting you will be in any way offended by seeing/shooting WW2 era Japanese firearms.
#2 you may even have the opportunity to check the translations of the characters stamped on the guns
#3 Japanese and Firearms are tied together by Movies, and I suspect while it wouldn't be mentioned to you, there would be a little let-down if at least a few iconic guns weren't present for being shot. I am sure a 44 magnum revolver would be a big hit, as would be even a 357 magnum, but also a Colt Single Action Army, and a 1911. But it wouldn't even have to be AMERICAN guns, a lot of german guns get screen time in movies, I am sure a Luger would be a great choice as well.
#4 Realize you aren't out to make 2nd amendment converts or to introduce shooting to people in a way that would make them want to join the hobby. If I was going to bring a group out to do this I'd want each attendee to have a LOT of trigger time as well as teaching them the basics of marksmanship etc, and having the assistance present to do this, which is generally 1 for every 2-3 shooters. Your situation is different. I would suggest bringing out one gun at a time for shooting. Take the gun out, talk about it a bit, let them see it, and then have them queue up to shoot it, just a few rounds and then on to the next person.
#5 Offer the opportunity for the shooters to pose with and be photographed with EVERY gun they shoot. 5 photos of shooting 2-3 rounds out of 5 different guns is probably a bigger deal than zero photos of shooting 100 rounds through 1 or 2 guns.