"Really? there is only 3 of them? I had the impression there were a LOT more than that."
Hi Joe! There will be a few more soon. FM satellites are useful because the ground equipment is fairly minimal (a duplex radio like a TH-D72, or a pair of HTs). BUT the big drawback is they support only one user at a time. The "linear" birds, of which there are many, support dozens of simultaneous users. The drawback is it requires more sophisticated radio gear because you need to use CW or SSB.
SO-50 is VERY easy to work. AO-85 (Fox1) is more challenging. The other FM bird is rarely turned on.
FM satellites on Field Day are a real challenge -- too many folks trying to work at one time.
Glad you had such a good time with the young ham. That's our future, and your time investment will pay off dividends down the road.
73, Bob, WB4SON