As far as the guns are concerned - It is the unsupervised access to the gun that is the problem with law enforcement. Since we’re talking about photo shoots and parents/guardians will be there anyway, that’s hardly an unsupervised environment. Where you could conceivably run into trouble is in the event of an accident with the weapon where someone is injured or worse. You would have to demonstrate that you’d taken reasonable precautions to prevent the accident from happening.
Lets face it... It's an imperfect world. People choke to death eating peanut butter in front of their TV's. Absolutely EVERYTHING you touch puts you at some kind of risk. Some things, of course, come with inherently more risk than others. There is, of course, a way to manage/minimize these risks. Where something like firearms are involved, I suggest you spend some time with someone who works with them in a professional capacity to develop a methodology and be absolutely certain that it is strictly adhered to at all times. (Please note: I do not necessarily mean a police officer. Some of them are competent. A very few are accomplished. Most, sadly, range between mediocre and completely inept.)
Since these are still pictures and not a movie, non-functional (demilled) firearms or replicas would be preferable. The problem with most “prop” type weapons is that they don’t look real. Non-firing replicas will look real and be safe at the same time. If you anticipate the need for such props with any regularity, I’d suggest you purchase some replicas and keep them on hand. If your concept does not require historical or contextual accuracy then one of the props would suffice. If, on the other hand, your concept does call for a specific firearm and a real one must be used then I really recommend having someone on set to exercise control over the handling of the weapons.
I am a competitive shooter and been involved in the defensive shooting arenas for quite some time. For the past two years I have been an assistant instructor for
John Farnam of Defense Training International, Inc. when he teaches in the Houston area. I also share instructor duties at weekly defensive shooting workshops at a local range. If you’d like, I’d be happy to work with you on such matters.