That is a loto f hand waving there.
The controllers on the switch are outright terrible, they all get the damn drift. The design of the controllers, while, small, are improperly shaped for small hands. The impossibility to tell which controller button to press due to having no letters on the left stick (the only one that fits small hands).
Then, the fact that changing controller order can put the switch in a state where only putting it to sleep allows to go back to the home and fix the order.
The thing the Switch has are extremely easy games, which is indeed good for young children. And some couch coop, which is great for brothers.
But the whole "change cartridge" is not helpful, children lose them (as they did with one of mine) and I had to withdraw access to those, since it's 50$ each. They now have to ask.
For the steam deck, set family view, parental controls and you CAN hide any games you want now.
If you connect the wireless controllers once to the steam deck (which can be connected to a tv), you are good to go, but you won't have games for them to play until they can properly read (6 or 7).
We are in a limbo where the gaming universe (not the tablet crap) is not properly developed for children yet.
lucky the accessibility options are moving things forward, but the reading requirement is really a big blocker.
I don't know why some games are tagged 3+ when the reading age for school is 6 (yes you can read earlier, but 6 is when you should be able to read)