Another option is mine: a Ruger SP101 and an H&R single shot in .357, cut down to "youth rifle" size. I'm still playing with handloads to see what the H&R will do. I've been experimenting with heavy bullet, subsonic loads. Low recoil and noise, and very cheap to shoot.
Standardizing could be a good way to save money for someone who wants to keep things simple. The .357 or .44 Magnum could both work for this. If you handload, costs could be kept fairly low, and both cartridges gain a lot in a rifle barrel.
All my best,
Dirty Bob