Well here is my experience with reduced loads. I highly doubt that your 12yr old or the 17yr old are going to be any worse off.
When my grandosn had just turned three, he said to me in a most serious tone, "I want to shoot me a hog Pawpaw." Now then, to know him when he was that age was really something. He had been in the woods with me since he was able to hold on to the gas cap of my 4 wheeler, and knew to cover his ears, or put on muffs whenever I hit the brakes hard, or reached for my little Ruger Compact chambered in .308. We did a regular hog patrol at a friends property to help them try and reduce the amount of damage they were doing to their pastures and fields. As such we were there about every weekend we could be and the grandson would miss any of it.
This said, when he made the above statement, I knew he meant it. I have a couple of .243's, one of which my daughter began hunting with at age 6. I had never loaded anything down, but in this case I knew I would have to. The deal is, if your going to shoot you have to hold the rifle. It's been that way since I was a youth and began hunting myself. Granted shots weren't going to be freehand, but he still needed to be able to hold and sight the rifle himself. As it turned out everything I had except the little Ruger simply weighed too much for him to hold up even with it on a rest. The barrels were too long and he simply couldn't overcome their effects. So I was left with him using my little six and a half pound .308 which I knew was going to kick no matter what. The stock is also thin so adding a recoil reduction tube was out of the question.
So with that in mind, and being that I have a couple of different calibers of Contender, I already had an idea that I wanted to use the 125 or 130gr bullets, but the question was from who. I settled on the Nosler Ballistic Tip as his shots were to be limited to 50yds max. I started with the Hodgdon data using H-4895, and even with the lowest charge weight, the first three shots really rocked his little world. Tears boiled up after each shot, but he was determined and we worked up to 5 shots, then 8 then 15 then what ever I had with me. We practiced all summer long when I could make it up to our farm, and I set out full sized deer targets with different angles and such so to make it more realistic. I set the out at different distances and would call out which one for him to shoot so he had to change positions and I would also count out loud so he had to make the shot count, withing a 5 count. Like I told him the deer and hogs aren't going to stand still so you have to be able to get on them, find your shot, and take it, within a minimal amount of time.
Two weeks before his 4th birthday, he dropped his first hog with one shot DRT. Then not long after he made a 158yd shot on a yote. The load had been increased to around 40 or 42 grains by then and the bullet did not exit the yote. It was at this point I switched over to the 130gr Barnes TTSX, and never looked back. I adjusted the load up to 42grs, and tried it myself out on hogs out to ranges of 200yds with shots from all different angles. It never failed to exit except on two out of over a dozen, and those were shot from the rear ham and the bullets lodged under the hide on their shoulder. Plenty for me, and he used them to get a few more hogs. This was all before his 8th birthday. Just after his eighth, and it being the week of Thanksgiving, he used his mom's 6.5x55 to take his first doe, then the next year the day after his 9th, he got his first buck with my old 25-06 that his mom used to get her first when she was 9. This year at 10 he used the same little Ruger again, only this time he had no issues with dropping the hammer on a factory loaded Remington 150gr CL.
With all this said, if you want to go with the reduced loads, that is fine, but work them up in a pretty fast amount. I know that rifle weight will soak up some, but you have to admit that my 6.5 pound fully loaded and ready to hunt rifle is going to have plenty more recoil on a 10yr old than a 12 or 17yr old. Still with H-4895 the recoil isn't bad even with a full load matching a factory 150gr CL. I just recently worked up a load with it and the 150gr CL's to match the factory loaded rounds. The difference in felt recoil is there for sure.
If it were me, I would simply purchase some of the bulk 150gr CL's and start off at the start data for H-4985 and let them go for it. I highly doubt that either will be put off by them, and even with this your already hitting much better numbers of velocity and energy than if you drop them down further. Those 150's will definitely get the job done as well, on most deer or hogs. I have taken hogs down with them at over 400yds that weighed over 400 pounds, and that is saying something for a bullet that is only running in the mid 2500fps range from my short 16.5" barrel.
Feel free to look at and show both of those youths the pictures of the grandson and some of his critters, they are all posted up on the bottom link under my sig. Tell them if he can do it so can you, heck your three times the age he was when he started, and shooting the same caliber rifle.
