Hi Isatje,
Yes, I frequently use Velleman kits and modules.
This forum community is very active and effective: do not hesitate to ask questions.
If you have questions on how to assemble the kit, the best advice I could give you is to follow the illustrated manual to the letter.
The trick to success for beginners is, by following the illustration, soldering first the component with low profiles (resistances, diodes…), and go to higher and higher profiles. By doing so, you’ll never have a component coming in your way.
And, furthermore, Velleman most often provides some small components on a tape (resitances, diodes), in the same order as they appear in the illustration. That way, they’re less risk of getting the wrong value at the wrong place.
One trick to speed up the process:
For resistances and diodes, you can insert 3 or 4 components on the board. Slightly bend the pins on the solder side, just enough to keep them in place when you tilt the board over. Then, solder one pin of one resistance, one pin of another resistance and so on. By doing so, especially for diodes, the component can cool down before you come to solder its second pin. This avoids bad surprises for beginners how are not accustomed with soldering, and who could sometimes overheat a component.
The same applies for transistors (3 pins) and even for the IC supports (Alternate a pin on one row, then a pin on the other row).
If your son is very young and/or a very beginner, I suggest he begins with simple kits so that he can practice how to make a good solder. By example, a Christmas tree or something like that (take a look at the Minikits series: there are some fun ones, with blinking lights and sound, and that’s always rewarding for a kid to have his first electronic assembly shining and tweeting 
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You can also download an illustrated assembly notice for any kit of the usual series: they feature a small tutorial on how to do good solder.
From my experience, I have never got a defective kit or component. But it has happened to me that by overheating a solder point, I broke a track and a solder pad.
If you have specific questions on how a given kit works, how you could modify one to adjust to specific needs, this forum is really a good place.
And people from Velleman are always very cool, and really are there to answer and help their customers
(Note: I’m not getting paid to say so many good things on Velleman… unfortunately 
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If you have specific questions you think I could help, please leave me a message in my PM box: I’ll be happy to help.
[Edit] Oops, there’s no Personnal Messages on this forum… I’ll send you a mail this evening.
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