I'm a traditionalist, chairman of my rifle club's Muzzle Loading division. I've been into muzzle loading since the 70's, have never built one from scratch but have assembled a few kits and always pleased with the outcome, you get out of them exactly what you put in. I've been working on one of Jim Kibler's Southern Mountain Rifle kits for some time now and have it assembled and am ready to apply finish to metal and wood.
If you youngster has an interest in working with metal and wood and/or has your experience and equipment to work with by all means get a kit, assemble the rifle and away you go, you could start something that could last his lifetime. With the limited time left as of this writing that's sorta out of the question.
I have never been interested reading any story involving the use of an in-line muzzle loader regardless the shooter. In-lines are modern rifles that load from the front, there is little romance, no historical significance, etc. However tell me story about a guy hunting moose with a flintlock in a swamp with a downpour of rain and I'm all ears.
Any one of the modern In-Lines will do the trick if all he wants to do is hunt a deer with a muzzle loader in the least amount of time, he might bruise his cheek a few times finding the right bullet/powder configuration but...he will likely move onto a cartridge rifle in the end, more range and accuracy potential.
Given time I would look into a nice kit, I'm personally sold on the Lyman GPR rifle. For the money they are the best off the shelf muzzle loaders I have ever owned or seen fired. In fact today a friend of mine that has considerable experience with dozens of muzzle loaders and owns dozens brought down a GPR he had paid $250 for and shot a five round group into one hole at 50 yards...his first time out. He just shot for group to see how it would do and it did just fine. Lyman makes kits in right and left hand, flintlock and percussion, they run around $600 if my memory serves me well. I bought one from a guy that had used it to hunt deer once for $300, put Lyman target sights on it and an L&R trigger and within a couple months was challenging the more experienced old hands with custom hand built guns to 1st place at matches.
The Pedersolis are nice rifles and are also made in Italy like the GPR. Track of the Wolf is an excellent resource, they also have completed rifles for sale, as does Buffalo Arms (a good source for Lyman kits)
The other issue is black powder, it has gotten difficult to obtain and expensive. There is only one store in town that sells black powder and currently it runs around $30 per pound which on average is around 100 shots with my .45 using between 55-85 gr. per shot @ 7000gr. to the lb. That's another part of the In-Line popularity, you can buy Pyrodex at nearly any sporting goods store, pellets or powder. The guys I shoot with all get together, we buy in bulk and got our last powder for $14 per pound, that is a significant savings, nearly half cost. We only shoot black powder and patched round ball, unless we are holding a rifled musket match, then black powder and minie bullet is the course, or round ball...some shoot patched round ball quite well.

If you want to pick my brain further P.M. me with any questions you would like answered in depth, I'll do what I can to help you out.

Dick