Some suggestions for Momof3: Connect with the National Muzzleloading Rifle Association (NMLRA) in Friendship, Indiana.
Type that title into your browser and go to their website. Among other things, they have a handout titled "Welcome To Muzzleloading" that is intended to help introduce beginners to the sport to the common types of ignition systems and how they work, basic loading and cleaning information and other tips. They're free, and designed to fold up into the users shirt pocket. There are more detailed sources of information that he can consult also, including this forum plus books available from the NMLRA, from Dixie Gun Works, and other ML supply houses, and also from bookstores and Amazon.com. The printed material will provide him with a handy reference source he can consult as often as he needs, make notes on, frame questions about, etc. The best source, as several others have mentioned, is folks who have been doing this stuff for more years than we care to admit and have made our mistakes, survived, have (mostly) learned from them, and are willing and eager to pass our hard-earned knowledge on to the next generations. One other thought: The NMLRA also sponsors Muzzleloading Hunter Safety courses that are required for most states' ML hunting seasons. The courses have a great deal of useful information for beginners and are well worth while. And of course, he'll have access to this forum, which provides access to many decades of muzzleloading experience and opinions. Especially opinions.
I also recommend the Dixie Gun Works catalog as a source of information. It's a wealth of lore on our sport as well as a good place to get just about anything a muzzleloader might need.
They have their stuff online too, but the paper catalog is a great read! Dixie is in Union City, Tennessee.
Good for you, for getting your son started.
Tanglefoot