Most likely, all you would be able to do with those is change out the HDD to SSD, if you haven't already, and possibly add more RAM.
There are a lot of similar models on the Lenovo, but I was seeing what looked like 2nd or 3rd get Intel CPU, and it looks like the Samsung is a 3rd gen i3?
I would probably consider loading W10 fresh on both of them. I would personally take some time to go through the machines OS and turn off/disable pretty much anything you can so far as background processes and items starting with Windows that don't hamper the desktop experience. Beyond that, I would create an Admin account to share with your brother/sister, and then create a standard user account for the nephews so they can't make system changes or install things (according to age, of course). Would probably run UAC up a notch as well. The 'rents might get tired of that after a while, so make sure to show them how to undo if they have the desire.
I would also create a backup just after the clean install and tune so that you can wipe and reinstall as is when they inevitable catch or download something that makes it "sick" (lol)