When you go to ASC, be sure to follow every range rule totheletter. Their range safety "officers" are range Nazis. And by all accounts they need to be -- lots of mishaps have occurred there.
You won't be drawing from a holster (you probably weren't planning to do so anyway, and there is absolutely no rapid fire allowed (again, probably not on your agenda). Just be prepared to follow a very regimented protocol -- which, again, is not a bad thing at a public range of that size. considered).
Your grandsons will learn a lot more about range safety, and be required to follow safety rules much more stringently than they would at some of the outdoor ranges in my area. And this is definitely a good thing.
I'll second what dawg23 said. You'll find it much more relaxed on the longer range rifle (200, 300) lanes, as there usually isn't a nazi there and you can run to the beat of your own drum. On the pistol lanes and <100yd rifle lanes it's somewhat silly. Show up, stand there for 20 minutes before you can put your target out, wait 10 minutes for every other bozo to get their target up, then wear your target out in 5-10 minutes and wait another 10-15 before you can retrieve it. The bullet holes in the roof are a telling sign that this is all very necessary.