Brian,
In the junior division of our gun club, we have been using Howard Leight's Max Lite low pressure foam earplugs. We have no connection to this manufacturer other than as satisfied users/coaches. We use the smaller size for the kids. I have personally tried them and found them to be somewhat more effective in reducing the sound of gunfire than the non-disposible plugs (a triple flanged model from Silencio) which I normally use. However my own plugs are much easier to seat, and are generally used in conjunction with ear muffs. Thus the combined hearing protection is normally ample.
I have found that when I use my custom fitted plugs under muffs they tend to work loose. However, I have not tried the custom units under the muffs without the connecting cord which may be contributing to the loosening. I tend to reserve the custom fitted plugs for hunting trips where circumstances make it difficult to also wear muffs.
I have cut the smaller foam plugs approximately in half lengthwise with scissors for my then 9 year old son. That allowed them to be seated well. They seemed to provide good hearing protection.
My family went to the drag races a few years ago. We all used plugs and muffs. We found that level of protection to be barely adequate. Indeed, at ground level next to the track near the starting line, the level of noise was sufficiently loud that we could feel the sound waves reverberating throughout our entire bodies. One remarkable discovery was that nearly 1/2 of the audience appeared to be using no hearing protection at all. There is much to be said for Darwin's theory of naturally selection. <img src="/images/graemlins/wink.gif" alt="" /> I also suspect that one could do a thriving business selling inexpensive hearing protectors. Come to think of it, our Boy Scout troop, or at least the friends thereof, could always use another fund-raiser.
It's fortunate that you were more knowledgeable than your former pediatrician. Incidentally, we found our otherwise very skilled and well-informed obstetrician to be admittedly ignorant about any potential deleterious effects of shooting on my then pregnant wife and unborn child.
Good luck,
John