I would recommend this article – https://golftips.golfweek.usatoday.com/select-junior-golf-clubs-20317.html Britt said everything well, and I completely agree with every word. But in this article everything is written more generally, maybe you will find more useful things there.
I am assuming you are wanting a “small set” for each of them. What you build and the specifications depend on several factors. Starting with the specifications, we have always fit juniors like adults with regards to length. There are charts that give you a range based on their height, but those are a guess at best. I would always prefer to have them set up so I could determine what length they need for any particular club or clubs. Of course you can get a length for a single iron and progress the remainder of the set off of that. The same for the woods. I am NOT an advocate of building them longer so they can “grow into them”. Does not allow them to develop, or it causes development of bad habits by swinging clubs that are too long. Fit them for the size they are now.
Another factor is the overall weight of the club. Do not want clubs that are too heavy. Although we can only do minor weight adjustments with the club heads, we can achieve a good overall weight by using lighter weight shafts. With the 14 year old, this may not be an issue if he is strong. I have seen a lot of strong 14 year olds that can handle standard weight clubs. I would evaluate what weight would be best, especially for the 10 year old girl. Too heavy, just like too long, prevents the development of good swing habits, results in poor results and can lead to discouragement.
One suggestion might be to simply start with a wedge, a 7 iron and maybe a #3 wood. That might not be enough and that is fine. You can start with as many clubs as you want. For the 10 year old girl, I would look at the M890 product we have. Woods, hybrids and irons are all available and we have the M890 graphite shafts that should be a good fit for her. For the 14 year old boy, you might look at the ST Series of product. Again, Woods, hybrids and irons available. Our MPF Series of graphite shafts would be good for his woods and hybrids and you could most likely use the True Temper Score steel iron shaft for his irons. You might also look at complete starter sets for specific age groups that are sold at Golf Galaxy and Dick’s Sporting Goods. Sometimes those are the best value. That being said, our product is a higher quality product and allows you much more flexibility in the process and how you introduce them to the different clubs in a set.
Hope this helps.